# -*- coding: utf-8 -*-

n = int(eval(input()))

a = [int(i) for i in input().split()]



"""

if len(set(a)) == len(a):

    print("YES")

else:

    print("NO")

"""



flag = True

a.sort()

for i in range(n - 1):

    if a[i] == a[i + 1]:

        flag = False

if flag:

    print("YES")

else:

    print("NO")

# -*- coding: utf-8 -*-

n = int(eval(input()))

a = [int(i) for i in input().split()] 



if len(set(a)) == n:

    print("YES")

else:

    print("NO")

# -*- coding: utf-8 -*-
n = int(eval(input()))
a = [int(i) for i in input().split()]
"""
if len(set(a)) == len(a):
    print("YES")
else:
    print("NO")
"""
flag = True
a.sort()
for i in range(n - 1):
    if a[i] == a[i + 1]:
        flag = False
if flag:
    print("YES")
else:
    print("NO")

# -*- coding: utf-8 -*-
n = int(eval(input()))
a = [int(i) for i in input().split()]
if len(set(a)) == n:
    print("YES")
else:
    print("NO")

-""" -if len(set(a)) == len(a): +if len(set(a)) == n: -""" -flag = True -a.sort() -for i in range(n - 1): -    if a[i] == a[i + 1]: -        flag = False -if flag: -    print("YES") -else: -    print("NO")