# coding: utf-8



import collections



n=int(eval(input()))

a_list=list(map(int,input().split()))



if len(collections.Counter(a_list))==len(a_list):

    print("YES")

else:

    print("NO")
# coding: utf-8



n=int(eval(input()))

a_list=list(map(int,input().split()))



if len(a_list)==len(set(a_list)):

    print("YES")

else:

    print("NO")
# coding: utf-8
import collections

n = int(eval(input()))
a_list = list(map(int, input().split()))
if len(collections.Counter(a_list)) == len(a_list):
    print("YES")
else:
    print("NO")

# coding: utf-8
n = int(eval(input()))
a_list = list(map(int, input().split()))
if len(a_list) == len(set(a_list)):
    print("YES")
else:
    print("NO")

-import collections - -if len(collections.Counter(a_list)) == len(a_list): +if len(a_list) == len(set(a_list)):