n,*a=map(int,open(0).read().split())
if len(a)==len(set(a)):
  print("YES")
else:
  print("NO") 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 if len(a)==len(set(a)):
  print("YES")
else:
  print("NO") len(a)==len(set(a)) len(a) len a len(set(a)) len set(a) set a print("YES") print "YES" print("NO") print "NO" n,*a=map(int,open(0).read().split()) map(int,open(0).read().split()) n
n,*a=map(int,open(0).read().split())
if len(a)==len(set(a)):
  print("YES")
else:
  print("NO")