from collections import Counter

N = int(input())
A = list(map(int, input().split()))
cnt = Counter(A)

for c in cnt.values():
    if c > 1:
        print("NO")
        exit()

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 c in cnt.values():
    if c > 1:
        print("NO")
        exit() c cnt.values() cnt.values cnt values if c > 1:
        print("NO")
        exit() c > 1 c 1 print("NO") print "NO" exit() exit print("YES") print "YES" A = list(map(int, input().split())) list(map(int, input().split())) A cnt = Counter(A) Counter(A) cnt N = int(input()) int(input()) N
from collections import Counter

N = int(input())
A = list(map(int, input().split()))
cnt = Counter(A)

for c in cnt.values():
    if c > 1:
        print("NO")
        exit()

print("YES")