import collections

N = int(input())
A = map(int, input().split())
answer = 'YES'
for v in collections.Counter(A).values():
    if v != 1:
        answer = 'NO'
        break
print(answer) import collections collections N = int(input()) N int(input()) int input() input A = map(int, input().split()) A map(int, input().split()) map int input().split() ().split () input split answer = 'YES' answer 'YES' for v in collections.Counter(A).values():
    if v != 1:
        answer = 'NO'
        break v collections.Counter(A).values() collections.Counter(A).values collections.Counter(A) collections.Counter collections Counter A values if v != 1:
        answer = 'NO'
        break v != 1 v 1 answer = 'NO' answer 'NO' break print(answer) print answer A = map(int, input().split()) map(int, input().split()) A N = int(input()) int(input()) N answer = 'NO' 'NO' answer answer = 'YES' 'YES' answer
import collections

N = int(input())
A = map(int, input().split())
answer = 'YES'
for v in collections.Counter(A).values():
    if v != 1:
        answer = 'NO'
        break
print(answer)
