import java.math.BigInteger; import java.util.Scanner; class Main { public static void main(String[] agrs) { Scanner scanner = new Scanner(System.in); BigInteger N = scanner.nextBigInteger(), i; scanner.close(); for (i = BigInteger.ONE.add(BigInteger.ONE); BigInteger.ONE.intValue() == N.compareTo(i); i = BigInteger.ONE.add(i)) { if (BigInteger.ZERO.equals(N.mod(i))) break; } if (N.equals(i)) System.out.print("YES"); else System.out.print("NO"); } }