n = gets.to_i
c = 0
n.times do |i|
c += 1 if n % (i+1) == 0
if
c > 2
break
end
end
if n == 1
  puts "NO"
elsif n == 2
  puts "YES"
elsif c == 3
  puts "YES"
elsif c == 2
  puts "NO"
end