import collections

N=int(input())
A=list(map(int,input().split()))
a=collections.Counter(A).most_common()
print("YES" if a[0][1]==1 else "NO") import collections collections 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 a=collections.Counter(A).most_common() a collections.Counter(A).most_common() collections.Counter(A).most_common collections.Counter(A) collections.Counter collections Counter A most_common print("YES" if a[0][1]==1 else "NO") print "YES" if a[0][1]==1 else "NO" a[0][1]==1 a[0][1] [0] a 0 1 1 "YES" "NO" a=collections.Counter(A).most_common() collections.Counter(A).most_common() a A=list(map(int,input().split())) list(map(int,input().split())) A N=int(input()) int(input()) N
import collections

N=int(input())
A=list(map(int,input().split()))
a=collections.Counter(A).most_common()
print("YES" if a[0][1]==1 else "NO")
