N,*a = map(int,open(0).read().split())
a.sort()
flag = True
for i in range(1,N):
  if a[i]==a[i-1]:
    print('NO')
    flag=False
    break
if flag ==True:
  print('YES') N,*a = map(int,open(0).read().split()) N map(int,open(0).read().split()) map int open(0).read().split() (0).read().split (0).read() (0).read (0) open 0 read split *a a a.sort() a.sort a sort flag = True flag True for i in range(1,N):
  if a[i]==a[i-1]:
    print('NO')
    flag=False
    break i range(1,N) range 1 N if a[i]==a[i-1]:
    print('NO')
    flag=False
    break a[i]==a[i-1] a[i] a i a[i-1] a i-1 i 1 print('NO') print 'NO' flag=False flag False break if flag ==True:
  print('YES') flag ==True flag True print('YES') print 'YES' flag = True True flag N,*a = map(int,open(0).read().split()) map(int,open(0).read().split()) N flag=False False flag
N,*a = map(int,open(0).read().split())
a.sort()
flag = True
for i in range(1,N):
  if a[i]==a[i-1]:
    print('NO')
    flag=False
    break
if flag ==True:
  print('YES')