from collections import Counter
n=int(input())
a=list(map(int, input().split()))

cnt=Counter(a)

for k in cnt.values():
    if k != 1:
        print('NO')
        break
else:
    print('YES') from collections import Counter n=int(input()) n int(input()) int input() input a=list(map(int, input().split())) a list(map(int, input().split())) list map(int, input().split()) map int input().split() ().split () input split cnt=Counter(a) cnt Counter(a) Counter a for k in cnt.values():
    if k != 1:
        print('NO')
        break
else:
    print('YES') k cnt.values() cnt.values cnt values if k != 1:
        print('NO')
        break k != 1 k 1 print('NO') print 'NO' break print('YES') print 'YES' cnt=Counter(a) Counter(a) cnt a=list(map(int, input().split())) list(map(int, input().split())) a n=int(input()) int(input()) n
from collections import Counter
n=int(input())
a=list(map(int, input().split()))

cnt=Counter(a)

for k in cnt.values():
    if k != 1:
        print('NO')
        break
else:
    print('YES')