import collections
N = int(input())
a = list(map(int,input().split()))
c = collections.Counter(a)

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

if c.most_common()[0][1]==1:
  print("YES")
else:
  print("NO")