#import math
import collections
#n,k = map(int, input().split( ))
#A = list(map(int, input().split( )))
n = int(input())
A = list(map(int, input().split( )))
c = collections.Counter(A)

a = c.most_common()[0][1]
if a != 1:
  print('NO')
else:
  print('YES') 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 a = c.most_common()[0][1] a c.most_common()[0][1] [0] c.most_common() c.most_common c most_common 0 1 if a != 1:
  print('NO')
else:
  print('YES') a != 1 a 1 print('NO') print 'NO' print('YES') print 'YES' c = collections.Counter(A) collections.Counter(A) c a = c.most_common()[0][1] c.most_common()[0][1] a A = list(map(int, input().split( ))) list(map(int, input().split( ))) A n = int(input()) int(input()) n
#import math
import collections
#n,k = map(int, input().split( ))
#A = list(map(int, input().split( )))
n = int(input())
A = list(map(int, input().split( )))
c = collections.Counter(A)

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