In a flower bed, there are N flowers, numbered 1,2,......,N. Initially, the heights of all flowers are 0. You are given a sequence h=\\{h_1,h_2,h_3,......\\} as input. You would like to change the height of Flower k to h_k for all k (1 \leq k \leq N), by repeating the following "watering" operation:

* Specify integers l and r. Increase the height of Flower x by 1 for all x such that l \leq x \leq r.



Find the minimum number of watering operations required to satisfy the condition.

Constraints

* 1 \leq N \leq 100
* 0 \leq h_i \leq 100
* All values in input are integers.

Input

Input is given from Standard Input in the following format:


N
h_1 h_2 h_3 ...... h_N


Output

Print the minimum number of watering operations required to satisfy the condition.

Examples

Input

4
1 2 2 1


Output

2


Input

5
3 1 2 3 1


Output

5


Input

8
4 23 75 0 23 96 50 100


Output

221
"""
8
4 23 75 0 23 96 50 100
"""

n = int(raw_input())
ais = map(int, raw_input().split(' '))

def f(ais):
	r = [0]
	for i in range(len(ais)):
		## looking for max
		if len(r) % 2:	
			if (ais[i-1] if i-1 >= 0 else 0) <= ais[i] > (ais[i+1] if i+1 < len(ais) else 0): 
				r.append(ais[i])
		else:
		## looking for min
			if (ais[i-1] if i-1 >= 0 else 0) >= ais[i] < (ais[i+1] if i+1 < len(ais) else 1000): 
				r.append(ais[i])

	t = 0
	for i in range(0,len(r),2):
		if i + 1 < len(r):
			u,v = r[i],r[i+1]
			t += v-u
	
	return t if len(ais) > 1 else ais[0]
print f(ais)