On her way to programming school tiger Dasha faced her first test — a huge staircase!

<image>

The steps were numbered from one to infinity. As we know, tigers are very fond of all striped things, it is possible that it has something to do with their color. So on some interval of her way she calculated two values — the number of steps with even and odd numbers. 

You need to check whether there is an interval of steps from the l-th to the r-th (1 ≤ l ≤ r), for which values that Dasha has found are correct.

Input

In the only line you are given two integers a, b (0 ≤ a, b ≤ 100) — the number of even and odd steps, accordingly.

Output

In the only line print "YES", if the interval of steps described above exists, and "NO" otherwise.

Examples

Input

2 3


Output

YES


Input

3 1


Output

NO

Note

In the first example one of suitable intervals is from 1 to 5. The interval contains two even steps — 2 and 4, and three odd: 1, 3 and 5.
'''
def main():
	from sys import stdin,stdout
if __name__=='__main__':
	main()
'''
# Journey to moon
'''
def main():
	from sys import stdin,stdout
	import collections
	N,I =map(int,stdin.readline().split())
	visited=list(0 for x in range(N))
	G=collections.defaultdict(list)
	groups=[0]
	for _ in range(I):
		a,b=map(int,stdin.readline().split())
		G[a].append(b)
		G[b].append(a)
	q=collections.deque()
	flag=0
	for i in range(N):
		if not visited[i]:
			q.append(i)
			visited[i]=flag+1
			groups[flag]+=1
			while len(q):
				top=q.popleft()
				for j in G[top]:
					if visited[j]!=visited[top]:
						visited[j]=flag+1
						groups[flag]+=1
						q.append(j)
			flag+=1
			groups.append(0)
	counter=0
	for i in range(len(groups)-1):
		for j in range(i+1,len(groups)):
			counter+=groups[i]*groups[j]
	stdout.write(str(counter))
if __name__=='__main__':
	main()
'''
# Djikstra's
'''
import collections
class Graph:
	def __init__(self):
		self.nodes=set()
		self.edges=collections.defaultdict(list)
		self.distances = {}

	def add_node(self, value):
		self.nodes.add(value)

	def add_edge(self, from_node, to_node, distance):
		self.edges[from_node].append(to_node)
		self.edges[to_node].append(from_node)
		self.distances[(from_node, to_node)] = distance
		self.distances[(to_node, from_node)] = distance


def dijsktra(graph, initial):
	visited = {initial: 0}
	path = {}

	nodes = set(graph.nodes)

	while nodes:
		min_node = None
		for node in nodes:
			if node in visited:
				if min_node is None:
					min_node = node
				elif visited[node] < visited[min_node]:
					min_node = node

		if min_node is None:
			break

		nodes.remove(min_node)
		current_weight = visited[min_node]

		for edge in graph.edges[min_node]:
			weight = current_weight + graph.distances[(min_node, edge)]
			if edge not in visited or weight < visited[edge]:
				visited[edge] = weight
				path[edge] = min_node

	return visited, path

def main():
	from sys import stdin,stdout
	for _ in range(int(stdin.readline())):
		n,m=map(int,stdin.readline().split())
		G=Graph()
		for i in range(n):
			G.add_node(i+1)
		for i in range(m):
			a,b,c=map(int,stdin.readline().split())
			G.add_edge(a,b,c)
		initial=int(stdin.readline())
		v,p=dijsktra(G, initial)
		#print(v)
		#print(p)
		for i in range(1,n+1):
			if i!=initial:
				k=v.get(i,-1)
				stdout.write(str(k)+' ')
		stdout.write('\n')
if __name__=='__main__':
	main()
'''
# Larget pallindrome in String
'''
def main():
	from sys import stdin,stdout
	string=stdin.readline().strip()
	l=len(string)
	#Triangle logic	
	
	arrlen=(l*(l-1))//2
	arr=list(0 for x in range(arrlen))
	f=0
	c=l-1
	for i in range(l-1):
		for j in range(i+1,l):
			if string[i]==string[j]:
				arr[f+j-i-1]=1
		f+=c
		c-=1
	#print(arr)
	if any(arr):
		
	else:
		if l & 1:
			stdout.write('First')
		else:
			stdout.write('Second')
	#2-d Array Logic
	arr=list(list(0 for i in range(l)) for j in range(l))
	for i in range(l):
		for j in range(l):
			if string[i]==string[j]:
				arr[i][j]=1
	maxim=0
	for i in range(0,l*(l-1)-2,l+1):
		a,b=i+1,i+2
		#print(a,b)
		acount=0
		x=a//5
		y=a%5
		acount=arr[x][y]		
		x-=1
		y-=1
		while x>=0 and y>=0:
			acount+=arr[x][y]
			x-=1
			y-=1
		x=b//5
		y=b%5
		bcount=arr[x][y]		
		x-=1
		y-=1
		while x>=0 and y>=0:
			bcount+=arr[x][y]
			x-=1
			y-=1
		maxim=max((acount,bcount,maxim))
	maxim=max(maxim,arr[l-2][l-1])
	maxim=(maxim<<1)^1
	delta=l-maxim
	if delta & 1:
		stdout.write('Second')
	else:
		stdout.write('First')
if __name__=='__main__':
	main()
'''
# 276B
'''
def main():
	from sys import stdin,stdout
	import collections
	s=stdin.readline().strip()
	count=collections.Counter(s)
	l=list(filter(lambda x: count[x] & 1,list(x for x in count)))
	removed=sum(list(count[x] for x in l))-max(list(count[x] for x in l)+[0])
	if removed & 1:
		stdout.write('Second')
	else:
		stdout.write('First')
if __name__=='__main__':
	main()
'''
# 362B
'''
def main():
	from sys import stdin,stdout
	n,m=map(int,stdin.readline().split())
	if m:
		dirty=sorted(map(int,stdin.readline().split()))
		if dirty[0]==1 or dirty[-1]==n:
			stdout.write('NO')
		else:
			flag=True
			for i in range(m-2):
				if dirty[i+1]==dirty[i]+1 and dirty[i+2]==dirty[i]+2:
					flag=False
					break
			if flag:
				stdout.write('YES')
			else:
				stdout.write('NO')
	else:
		stdout.write('YES')
if __name__=='__main__':
	main()
'''
# 279B SUM OF SUB-ARRAY
'''
def main():
	from sys import stdin,stdout
	n,t=map(int,stdin.readline().split())
	arr=list(map(int,stdin.readline().split()))
	maxim=0
	curr_sum=arr[0]
	i=0
	j=1
	if curr_sum <=t:
		count=1
	else:
		curr_sum=0
		count=0
		i=1
		j=2
	while j<n:
		if curr_sum+arr[j]<=t:
			count+=1
			curr_sum+=arr[j]
			j+=1
		else:
			maxim=max(count,maxim)
			if curr_sum:
				curr_sum-=arr[i]
				count-=1
			else:
				j+=1
			i+=1
	maxim=max(count,maxim)
	stdout.write(str(maxim))
if __name__=='__main__':
	main()
'''
# 469B
'''
def main():
	from sys import stdin,stdout
	p,q,l,r=map(int,stdin.readline().split())
	a=[]
	b=[]
	visited=list(0 for x in range(r-l+1))
	#print(visited)	
	for i in range(p):
		x,y=map(int,stdin.readline().split())
		a.append(x)
		b.append(y)
	for i in range(q):
		x,y=map(int,stdin.readline().split())
		x+=l
		y+=l
		for j in range(p):
			#print('x=',x,'y=',y)
			lower=max(0,a[j]-y)
			upper=min(b[j]-x,r)+1
			if upper > lower:
				delta=upper-lower
				#print('upper=',upper,'lower=',lower)
				visited[lower:upper]=list(1 for x in range(delta))
				#print('visited:\n',visited)
	#	print(visited)
	stdout.write(str(visited[:r-l+1].count(1)))
if __name__=='__main__':
	main()
'''
'''
def main():
	from sys import stdin,stdout
	#import numpy as np
	n,k=map(int,stdin.readline().split())
	a=tuple(map(int,stdin.readline().split()))
	minim=min(a)
	maxim=max(a)
	arr=list(a)	
	for i in range(n):
		arr[i]-=minim
	if max(arr) > k:
		stdout.write('NO')
	else:
		stdout.write('YES\n')
		for i in a:
			stdout.write('1 '*minim)
			for j in range(i-minim):
				stdout.write(str(j%k+1)+' ')
			stdout.write('\n')
if __name__=='__main__':
	main()
'''
'''
def main():
	from sys import stdin,stdout
	n,p=[],[]
	for _ in range(int(stdin.readline())):
		last=int(stdin.readline())
		if last<0:
			n.append(-1*last)
		else:
			p.append(last)
	if sum(p)>sum(n):
		stdout.write('first')
	elif sum(n)>sum(p):
		stdout.write('second')
	else:
		maxim=max(n,p)
		#print(maxim)
		if maxim==p:
			if maxim==n:
				if last<0:
					stdout.write('second')
				else:
					stdout.write('first')
			else:
				stdout.write('first')
		else:
			stdout.write('second')
		
if __name__=='__main__':
	main()
'''
# 286C
'''
def main():
	from sys import stdin,stdout
	m,n=map(int,stdin.readline().split())
	minim=min(m,n)
	stdout.write(str(minim+1)+'\n')
	if n==minim:
		for i in range(minim+1):
			stdout.write(str(m)+' '+str(i)+'\n')
			m-=1
	else:
		for i in range(minim+1):
			stdout.write(str(i)+' '+str(n)+'\n')
			n-=1
if __name__=='__main__':
	main()
'''
# 387B
'''
def main():
	from sys import stdin,stdout
	n,m=map(int,stdin.readline().split())
	a=tuple(map(int,stdin.readline().split()))
	b=tuple(map(int,stdin.readline().split()))
	i=0
	j=0
	while True:
		#print(i,j)
		if i>=n or j>=m:
			break
		if b[j]>=a[i]:
			i+=1
			j+=1
		else:
			j+=1
	stdout.write(str(n-i))
if __name__=='__main__':
	main()
'''
# 365B
'''
def main():
	from sys import stdin,stdout
	n=int(stdin.readline())
	a=tuple(map(int,stdin.readline().split()))
	maxim=2
	count=2
	i=2
	while True:
		if i>=n:
			break
		if a[i]==a[i-1]+a[i-2]:
			count+=1
			maxim=max(count,maxim)
		else:
			count=2
		i+=1
	stdout.write(str(min(maxim,n)))
if __name__=='__main__':
	main()
'''  # 474D
'''
def main():
	from sys import stdin,stdout
	MOD=int(1e9)+7
	T,k=map(int,stdin.readline().split())
	fib=[x for x in range(1,k+1)]
	for i in range(k,100001):
		fib.append((fib[i-1]+fib[i-k]+1)%MOD)
	for _ in range(T):
		a,b=map(int,stdin.readline().split())
		stdout.write(str((fib[b]-fib[a-1])%MOD)+'\n')
if __name__=='__main__':
	main()
'''
# 330B
# not working
'''
def main():
	from sys import stdin,stdout
	import collections
	road_not=collections.defaultdict(set)
	n,m=map(int,stdin.readline().split())
	for _ in range(m):
		a,b=map(int,stdin.readline().split())
		road_not[a].add(b)
		road_not[b].add(a)
	counter=0
	road=collections.defaultdict(set)
	visited=[0 for x in range(n)]
	visited[0]=True
	for index in range(1,n+1):
		for i in range(1,n+1):
			if not visited[i-1]:
				if i not in road_not[index] and i!=index:
					counter+=1
					road[index].add(i)
					visited[i-1]=True
	stdout.write(str(counter)+'\n')
	for i in road:
		for j in road[i]:
			stdout.write(str(i)+' '+str(j)+'\n')
if __name__=='__main__':
	main()
'''
# 208D
'''
def main():
	from sys import stdin,stdout
	import bisect
	n=int(stdin.readline())
	p=tuple(map(int,stdin.readline().split()))
	P=tuple(map(int,stdin.readline().split()))
	record=[0 for x in range(5)]
	points=0
	for i in p:
		points+=i
		while points>=P[0]:
			index=bisect.bisect_right(P,points)
			if index:
				index-=1
				number=points//P[index]
				record[index]+=number
				points-=P[index]*number
	for i in record:
		stdout.write(str(i)+' ')
	stdout.write('\n'+str(points))
if __name__=='__main__':
	main()
'''
# 339D Using Al.Cash's Segment Trees
# Segment Tree
# not-working
'''
powers=1
t=[0 for x in range(3*int(1e5))]
def build(n):
	global t,powers
	flag=False
	for i in range(n-1,0,-1):
		if i==powers-1:
			flag=not flag
			powers>>=1
		if flag:
			t[i]=t[i<<1]^t[i<<1|1]
		else:
			t[i]=t[i<<1]|t[i<<1|1]

def modify(i,v,n):
	global t
	flag=False
	if t[i+n-1]==v or v|t[(i+n-1)^1]==t[(i+n-1)>>1]:
		#print('skipped')
		#print('t[i+n-1]=',t[i+n-1],'v=',v)
		#print('v|t[(i+n-1)^1]=',v|t[(i+n-1)^1],'t[(i+n-1)>>1]',t[(i+n-1)>>1])		
		t[i+n-1]=v		
		return
	t[i+n-1]=v
	p=i+n-1
	while p>1:
		if flag:
			if t[p>>1]==t[p]^t[p^1]:
				break
			t[p>>1]=t[p]^t[p^1]
			flag=not flag
		else:
			if t[p>>1]==t[p]|t[p^1]:
				break
			t[p>>1]=t[p]|t[p^1]
			flag=not flag
		p>>=1

def main():
	from sys import stdin,stdout
	global t,powers
	n,m=map(int,stdin.readline().split())
	p=tuple(map(int,stdin.readline().split()))
	powers=1<<(n-1)	
	n=1<<(n)	
	for i in range(n):
		t[i+n]=p[i]
	build(n)
	#print(t[:2*n])
	for _ in range(m):
		a,b=map(int,stdin.readline().split())
		modify(a,b,n)
		#print(t[:2*n])
		stdout.write(str(t[1])+'\n')
if __name__=='__main__':
	main()
'''
# 330B
'''
def main():
	from sys import stdin,stdout
	n,m=map(int,stdin.readline().split())
	start_not=set()
	for _ in range(m):
		a,b=map(int,stdin.readline().split())
		start_not.add(a-1)
		start_not.add(b-1)
	visited=[False for _ in  range(n)]
	for i in range(n):
		if i not in start_not:
			center=i
			break
	stdout.write(str(n-1)+'\n')
	for i in range(n):
		if i != center:
			stdout.write(str(center+1)+' '+str(i+1)+'\n')
if __name__=='__main__':
	main()
'''
# 116B
'''
def main():
	from sys import stdin,stdout
	n,m=map(int,stdin.readline().split())
	arr=[]
	for _ in range(n):
		arr.append(stdin.readline().strip())
	pigs=set()
	count=0
	for i in range(n):
		for j in range(m):
			if arr[i][j]=='W':
				flag=0
				if i>0:
					if arr[i-1][j]=='P':
						pigs.add((i-1,j))
						flag=1
				if i<n-1:
					if arr[i+1][j]=='P':
						pigs.add((i+1,j))
						flag=1
				if 	j>0:
					if arr[i][j-1]=='P':
						pigs.add((i,j-1))
						flag=1
				if j<m-1:
					if arr[i][j+1]=='P':
						pigs.add((i,j+1))
						flag=1
				if flag:
					count+=1
	stdout.write(str(min(len(pigs),count)))
if __name__=='__main__':
	main()
'''
# 339D using Al.Cash's Segment Tree Implementation
'''
def power(a,b):
	if b:
		if b &1:
			return a*power(a,b-1)
		else:
			return power(a*a,b//2)
	else:
		return 1;
def main():
	from sys import stdin,stdout
	answers=()
	n,m=map(int,stdin.readline().split())
	p=tuple(map(int,stdin.readline().split()))
	powers=power(2,n-1)
	n=powers<<1
	t=[0 for _ in range(n<<1)]
	for i in range(n):
		t[n+i]=p[i]
	flag=False
	for i in range(n-1,0,-1):
		if i==powers-1:
			flag=not flag
			powers>>=1
		if flag:
			t[i]=t[i<<1]^t[i<<1|1]
		else:
			t[i]=t[i<<1]|t[i<<1|1]
	for _ in range(m):
		a,b=map(int,stdin.readline().split())
		flag=False
		if t[a+n-1]==b or b|t[(a+n-1)^1]==t[(a+n-1)>>1]:
			t[a+n-1]=b
		else:
			t[a+n-1]=b
			p=a+n-1
			while p > 1:
				if flag:
					if t[p>>1]==t[p]^t[p^1]:
						break
					t[p>>1]=t[p]^t[p^1]
					flag=not flag
				else:
					if t[p>>1]==t[p]|t[p^1]:
						break
					t[p>>1]=t[p]|t[p^1]
					flag= not flag
				p>>=1
		stdout.write(str(t[1])+'\n')
if __name__=='__main__':
	main()
'''
# 515C
'''
def main():
	from sys import stdin,stdout
	import collections
	nc=[0 for x in range(10)]
	n=int(stdin.readline())
	num=stdin.readline().strip()
	for i in num:
		k=int(i)
		if k==9:
			nc[7]+=1
			nc[3]+=2
			nc[2]+=1
		elif k==8:
			nc[7]+=1
			nc[2]+=3
		elif k==7:
			nc[7]+=1
		elif k==6:
			nc[5]+=1
			nc[3]+=1
		elif k==5:
			nc[5]+=1
		elif k==4:
			nc[3]+=1
			nc[2]+=2
		elif k==3:
			nc[3]+=1
		elif k==2:
			nc[2]+=1
	ans=''
	for i in range(10):
		ans+=str(9-i)*nc[9-i]
	stdout.write(ans)		
if __name__=='__main__':
	main()
'''
# 313B
'''
def main():
	from sys import stdin,stdout
	s=stdin.readline().strip()
	flag=s[0]
	if flag=='.':
		anti='#'
	else:
		anti='.'
	n=len(s)
	l=[0 for x in range(n)]
	for i in range(1,n):
		if s[i]==flag:
			l[i]=l[i-1]+1
		else:
			flag,anti=anti,flag
			l[i]=l[i-1]
	#print(l)
	for _ in range(int(stdin.readline())):
		a,b=map(int,stdin.readline().split())
		stdout.write(str(l[b-1]-l[a-1])+'\n')
if __name__=='__main__':
	main()
'''
# 431C
'''
def main():
	from sys import stdin,stdout
	MOD=int(1e9)+7
	n,k,d=map(int,stdin.readline().split())
	d-=1
	klist=[(1<<i)%MOD for i in range(k)]
	klist=[1]+klist
	for i in range(k+1,n+1):
		klist.append((klist[i-1]*2-klist[i-1-k])%MOD)
	if d:	
		dlist=[(1<<i)%MOD for i in range(d)]
		dlist=[1]+dlist
		for i in range(d+1,n+1):
			dlist.append((dlist[i-1]*2-dlist[i-1-d])%MOD)
	#print(klist)
	#print(dlist)
		ans=klist[n]-dlist[n]
	else:
		ans=klist[n]
	stdout.write(str(ans%MOD))
if __name__=='__main__':
	main()
'''
# 441C
'''
def main():
	from sys import stdin,stdout
	n,m,k=map(int,stdin.readline().split())
	if n>=m:
		i=-1
		j=-1
		num=n*m
		while k:
			ans=num//k
			stdout.write(str(ans)+' ')
			counter=0
			while counter<ans:
				if j==-1:
					flag=True
					i+=1
					j+=1
				if j==m:
					flag=False
					i+=1
					j-=1
				stdout.write(str(i+1)+' '+str(j+1)+' ')
				if flag:
					j+=1
				else:
					j-=1
				counter+=1
			num-=ans
			k-=1
			stdout.write('\n')
	else:
		i=-1
		j=-1
		num=n*m
		while k:
			ans=num//k
			stdout.write(str(ans)+' ')
			counter=0
			while counter<ans:
				if i==-1:
					flag=True
					j+=1
					i+=1
				if i==n:
					flag=False
					j+=1
					i-=1
				stdout.write(str(i+1)+' '+str(j+1)+' ')
				if flag:
					i+=1
				else:
					i-=1
				counter+=1
			num-=ans
			k-=1
			stdout.write('\n')
if __name__=='__main__':
	main()
'''
# 538B
'''
def main():
	from sys import stdin,stdout
	n=int(stdin.readline())
	ans=[]
	while n:
		t=''
		num=str(n)
		for i in num:
			if int(i):
				t+='1'
			else:
				t+='0'
		ans.append(t)
		n-=int(t)
	stdout.write(str(len(ans))+'\n')
	for i in ans:
		stdout.write(i+' ')
if __name__=='__main__':
	main()
'''
# 486C
# Palidrome Transformation
'''
def main():
	from sys import stdin,stdout
	n,o=map(int,stdin.readline().split())
	string=stdin.readline().strip()
	if n & 1:
		s1=string[:n//2]
		s2=string[n//2+1:]
		rev=s2[::-1]
		minim=0
		indexlist=[]
		for i in range(n//2):
			k=abs(ord(s1[i])-ord(rev[i]))
			minim+=min(k,26-k)
			if k:
				indexlist.append(i)
		if o>n//2:
			o=(n-o)
		else:
			o-=1
		if len(indexlist):
			indexlist+=[o]
			for i in range(len(indexlist)):
				indexlist[i]=indexlist[i]-o
			minia=min(indexlist)
			maxia=max(indexlist)
			minim+=min(abs(minia),abs(maxia))*2+max(abs(minia),abs(maxia))
		stdout.write(str(minim))
	else:
		s1=string[:n//2]
		s2=string[n//2:]
		rev=s2[::-1]
		#print(s1,rev)
		minim=0
		indexlist=[]
		for i in range(n//2):
			k=abs(ord(s1[i])-ord(rev[i]))
			minim+=min(k,26-k)
			if k:
				indexlist.append(i)
		if o > n//2:
			o=(n-o)
		else:
			o-=1
		#print(minim)
		#print(indexlist)
		if len(indexlist):
			indexlist+=[o]
			for i in range(len(indexlist)):
				indexlist[i]=indexlist[i]-o
			#print(indexlist)
			minia=min(indexlist)
			maxia=max(indexlist)
			minim+=min(abs(minia),abs(maxia))*2+max(abs(minia),abs(maxia))
		stdout.write(str(minim))
if __name__=='__main__':
	main()
'''
# 4B
'''
def main():	
	from sys import stdin,stdout
	n,sumtime=map(int,stdin.readline().split())
	a,b=[],[]
	for i in range(n):
		x,y=map(int,stdin.readline().split())
		a.append(x)
		b.append(y)
	if sum(b)<sumtime or sum(a)>sumtime:
		stdout.write('NO')
	else:
		stdout.write('YES\n')
		diff=sumtime-sum(a)
		for i in range(n):
			if diff:
				k=b[i]-a[i]
				minim=min(k,diff)
				a[i]+=minim
				diff-=minim
		for i in a:
			stdout.write(str(i)+' ')
if __name__=='__main__':
	main()
'''
# 282B
'''
def main():
	from sys import stdin,stdout
	n=int(stdin.readline())
	a,b=[],[]
	for i in range(n):
		x,y=map(int,stdin.readline().split())
		a.append(x)
		b.append(y)
	if a[0]>b[0]:
		total=-1*b[0]
		t='G'
	else:
		total=a[0]
		t='A'
	for i in range(1,n):
		if total+a[i]>=500:
			total-=b[i]
			t+='G'
		else:
			total+=a[i]
			t+='A'
	if total<-500 or total >500:
		stdout.write('-1')
	else:
		stdout.write(t)
if __name__=='__main__':
	main()
'''
# 122B
'''
def main():
	from sys import stdin,stdout
	s=stdin.readline().strip()
	for i in s:
		if i=='0':
			s=s[1:]
		else:
			break
	count4=s.count('4')
	count7=s.count('7')
	if count4 or count7:
		if count4>=count7:
			stdout.write('4')
		else:
			stdout.write('7')
	else:
		stdout.write('-1')
if __name__=='__main__':
	main()
'''
# 155B
'''
def main():
	from sys import stdin,stdout
	a,b=[],[]
	n=1
	total=int(stdin.readline())
	for _ in range(total):
		x,y=map(int,stdin.readline().split())
		n+=y
		if y:
			a.append(x)
		else:
			b.append(x)	
	a.sort(reverse=True)
	b.sort(reverse=True)
	alen=len(a)
	blen=len(b)
	minim=min(total,n)
	points=0
	if minim>alen:
		extra=minim-alen
		points+=sum(a)
		points+=sum(b[:extra])
	else:
		points=sum(a[:minim])
	stdout.write(str(points))
if __name__=='__main__':
	main()
'''
# 368B
'''
def main():
	from sys import stdin,stdout
	import collections
	n,m=map(int,stdin.readline().split())
	arr=list(map(int,stdin.readline().split()))
	s=set()
	ans=collections.deque([0])
	for i in range(n-1,-1,-1):
		if arr[i] in s:
			ans.appendleft(ans[0])
		else:
			ans.appendleft(ans[0]+1)
			s.add(arr[i])
	for _ in range(m):
		a=int(stdin.readline())-1
		stdout.write(str(ans[a])+'\n')
if __name__=='__main__':
	main()
'''
# 166E
''''
def main():
	from sys import stdin,stdout
	MOD=int(1e9)+7
	n=int(stdin.readline())
	if n&1:
		ans=0
		flag=3
		for _ in range(1,n,2):
			ans=(ans+flag)%MOD
			flag=(flag*9)%MOD
		ans<<=1
		stdout.write(str((ans)%MOD))
	else:
		ans=0
		flag=9
		for _ in range(2,n,2):
			ans=(ans+flag)%MOD
			flag=(flag*9)%MOD
		ans<<=1
		ans+=3
		stdout.write(str((ans)%MOD))
if __name__=='__main__':
	main()
'''
'''
# 352B
def main():
	from sys import stdin, stdout
	import collections
	n = int(stdin.readline())
	t=tuple(map(int,stdin.readline().split()))
	dic=collections.defaultdict(list)
	for i in range(n):
		dic[t[i]].append(i)
	counter=0
	for i in dic:
		mylist=dic[i]
		if len(mylist)==1:
			counter+=1
		else:
			c=mylist[1]-mylist[0]
			flag=True
			for j in range(2,len(mylist)):
				if mylist[j]-mylist[j-1]!=c:
					flag=False
					break
			if flag:
				counter+=1
	stdout.write(str(counter)+'\n')
	for i in sorted(dic):
		mylist = dic[i]
		if len(mylist) == 1:
			stdout.write(str(i)+' 0\n')
		else:
			c = mylist[1] - mylist[0]
			flag = True
			for j in range(2, len(mylist)):
				if mylist[j] - mylist[j - 1] != c:
					flag = False
					break
			if flag:
				stdout.write(str(i)+' '+str(c)+'\n')
if __name__ == '__main__':
	main()
'''
'''
def main():
	from sys import stdin,stdout
	dic={'>':'1000','<':'1001','+':'1010', '-':'1011', '.':'1100',',':'1101','[':'1110',']':'1111'}
	s=stdin.readline().strip()
	t=''
	for i in s:
		t+=dic[i]
	num=int(t,2)
	stdout.write(str(num%(int(1e6)+3)))
if __name__=='__main__':
	main()
'''
#567C
'''
def main():
	from sys import stdin,stdout
	import collections
	import bisect
	index=collections.defaultdict(list)
	n,k=map(int,stdin.readline().split())
	t=tuple(map(int,stdin.readline().split()))
	for i in range(n):
		index[t[i]].append(i)
	mycounter=collections.Counter(t)
	print(mycounter)
	print(index)
	index=dict(index)
	counter=0
	flag=True
	for i in index:
		for j in index[i]:
			c=1
			n=index.get(i*k,[])
			if len(n):
				c*=(len(n)-bisect.bisect_left(n,j))
			else:
				flag=False
				break
			n=index.get(i*k*k,[])
			if len(n):
				c*=(len(n)-bisect.bisect_left(n,j))
			else:
				flag=False
				break
			counter+=c
			print(i,j,counter)
		if not flag:
			break
	stdout.write(str(counter))
if __name__=='__main__':
	main()
'''
'''
def main():
	from sys import stdin,stdout
	n,o1,o2=map(int,stdin.readline().split())
	m=set()
	for _ in range(n):
		a,b=map(int,stdin.readline().split())
		d1=a-o1
		d2=b-o2
		if d2:
			m.add(d1/d2)
		else:
			m.add('inf')
	stdout.write(str(len(m)))
if __name__=='__main__':
	main()
'''
#4C
'''
def main():
	from sys import stdin,stdout
	import collections
	namecounter=collections.Counter()
	for _ in range(int(stdin.readline())):
		ip=stdin.readline().strip()
		k=namecounter[ip]
		namecounter[ip]+=1
		if k:
			stdout.write(ip+str(k)+'\n')
		else:
			stdout.write('OK\n')
if __name__=='__main__':
	main()
'''
#363C
'''
def main():
	from sys import stdin,stdout
	ip=stdin.readline().strip()
	t=ip[0]
	for ch in ip[1:]:
		if len(t)>2:
			if (ch==t[-1] and t[-2]==t[-3] ) or (ch==t[-1] and t[-1]==t[-2]):
				continue
			else:
				t+=ch
		elif len(t)==2:
			if ch==t[-1] and ch==t[-2]:
				continue
			else:
				t+=ch
		else:
			t+=ch
	stdout.write(t)
if __name__=='__main__':
	main()
'''
#490C
#(STRING to NUMBER)DIGITS
#not working
'''
def main():
	from sys import stdin,stdout
	import bisect
	A=set()
	B=set()
	anum=0
	bnum=0
	p=1
	flag=False		
	s=stdin.readline().strip()
	a,b=map(int,stdin.readline().split())
	length=len(s)
	for i in range(length):
		n=ord(s[i])-48
		m=ord(s[length-i-1])-48
		anum=anum*10+n
		bnum=m*p+bnum
		if anum % a==0:
			A.add(i)
		if bnum % b==0:
			B.add(length-i-1)
		p*=10
	if len(A) and len(B):
		for i in A:
			if i<length-1:
				if i+1 in B and s[i+1]!='0':
					flag=True
					break
	if flag:
		stdout.write('YES\n'+s[:i+1]+'\n'+s[i+1:])
	else:
		stdout.write('NO')	
if __name__=='__main__':
	main()
'''
#Round-392
#758A
'''
def main():
	from sys import stdin,stdout
	n=int(stdin.readline())
	a=tuple(map(int,stdin.readline().split()))
	maxim=max(a)
	mysum=0
	for i in a:
		mysum+=(maxim-i)
	stdout.write(str(mysum))
if __name__=='__main__':
	main()
'''
#758B
'''
def main():
    from sys import stdin,stdout
    import collections
    counter=collections.Counter()
    s=list(stdin.readline().strip())
    for i in range(len(s)):
        if s[i]=='!':
            if i-4<0:
                if s[i+4]!='!':
                    counter[s[i+4]]+=1
                    s[i]=s[i+4]
                else:
                    sample=s[i:i+4]
                    for i in 'RBYB':
                        if i not in sample:
                            break
                    counter[i]+=1
                    s[i]=i
            else:
                if s[i-4]!='!':
                    counter[s[i-4]]+=1
                    s[i]=s[i-4]
                elif i+4<n:
                    if s[i+4]!='!':
                        counter[s[i+4]]+=1
                        s[i]=s[i+4]
    for i in 'RBYG':
        stdout.write(str(counter[i])+' ')
if __name__=='__main__':
    main()
'''
#758D
'''
def main():
    from sys import stdin,stdout
    base=int(stdin.readline())
    n=stdin.readline().strip()
    revn=n[::-1]
    p=1
    i=len(n)-2
    num=int(revn[0])
    ans=0
    while i>=0:
        if revn[i]=='0':
            if num or i==1:
                ans+=num*p
                p*=base
            p*=base
            num=0
            i+=1
            continue
        if num:
            ch=int(revn[i])*10+num
        else:
            ch=int(revn[i])
        if ch < base:
            num=ch
            i+=1
        else:
            ans+=num*p
            p*=base
            num=0
    if num:
        ans+=num*p
    stdout.write(str(ans))
if __name__=='__main__':
    main()
'''
#626B
'''
def main():
	from sys import stdin,stdout
	import collections
	n=int(stdin.readline())
	s=stdin.readline().strip()
	counter=collections.Counter(s)
	temp=''
	for i in 'BGR':
		if not counter[i]:
			temp+=i
	if len(temp)==2:
		if n>1:
			stdout.write(str(counter.most_common(1)[0][0]))
		else:
			stdout.write(s)
	elif len(temp)==1:
		if n>2:
			ans=list(temp+str(counter.most_common(2)[1][0]))
			ans.sort()
			stdout.write(''.join(x for x in ans))
		else:
			stdout.write(temp)
	else:
		stdout.write('BGR')
if __name__=='__main__':
	main()
'''
#650A
'''
def man(a,b):
	return abs(a[0]-b[0])+abs(a[1]-b[1])
def euc(a,b):
	if a[0]==b[0]:
		return abs(a[1]-b[1])
	elif a[1]==b[1]:
		return abs(a[0]-b[0])
	else:
		return 0
def main():
	from sys import stdin,stdout
	import collections
	counter=collections.Counter()
	xcounter=collections.Counter()
	ycounter=collections.Counter()
	n=int(stdin.readline())
	for _ in range(n):
		x,y=map(int,stdin.readline().split())
		counter[(x,y)]+=1
		xcounter[x]+=1
		ycounter[y]+=1
	ans=0
	for i in xcounter:
		ans+=(xcounter[i]*(xcounter[i]-1))//2
	for i in ycounter:
		ans+=(ycounter[i]*(ycounter[i]-1))//2
	for i in counter:
		ans-=(counter[i]*(counter[i]-1))//2
	stdout.write(str(ans))
if __name__=='__main__':
	main()
'''
#522B
'''
def main():
	from sys import stdin,stdout
	w=[]
	h=[]
	width_sum=0
	maxim=-100
	for _ in range(int(stdin.readline())):
		x,y=map(int,stdin.readline().split())
		w.append(x)
		h.append(y)
		width_sum+=x
		if y>maxim:
			maxim=y
			maxindex=_
	maxim1=maxim
	maxim2=max(h[:maxindex]+h[maxindex+1:])
	for i in range(len(w)):
		if i==maxindex:
			stdout.write(str((width_sum-w[i])*maxim2)+' ')
		else:
			stdout.write(str((width_sum-w[i])*maxim1)+' ')
if __name__=='__main__':
	main()
'''
#343B
'''
def main():
	from sys import stdin,stdout
	#import collections
	s=stdin.readline().strip()
	#ans=collections.deque(('\0'))
	t=('\0',)
	flag=t[-1]
	for i in s:
		if flag==i:
			t=t[:-1]
		else:
			t+=(i,)
		flag=t[-1]
		#print(t )
	if t==('\0',):
		stdout.write('yes')
	else:
		stdout.write('no')
if __name__=='__main__':
	main()
'''
#761
#A

def main():
	from sys import stdin,stdout
	a,b=map(int,stdin.readline().split())
	if a and b:
		if abs(a-b)>1:
			stdout.write('NO')
		else:
			stdout.write('YES')
	else:
		if abs(a-b)>1:
			stdout.write('NO')
		else:
			if a or b:
				stdout.write('YES')
			else:
				stdout.write('NO')
if __name__=='__main__':
	main()
#B
'''
def main():
	from sys import stdin,stdout
	n,l=map(int,stdin.readline().split())
	a=list(map(int,stdin.readline().split()))
	b=list(map(int,stdin.readline().split()))
	ansa=[]
	ansb=[]
	for i in range(1,n):
		ansa.append(a[i]-a[i-1])
		ansb.append(b[i]-b[i-1])
	ansa.append(a[0]+(l-a[-1]))
	ansb.append(b[0]+(l-b[-1]))
	ansa.sort()
	ansb.sort()
	if ansa==ansb:
		stdout.write('YES')
	else:
		stdout.write('NO')
if __name__=='__main__':
	main()
'''
