import java.math.BigInteger; import java.util.Scanner; public class Main { public static void main(String[] args) { Scanner sc = new Scanner(System.in); BigInteger H = new BigInteger(sc.next()); BigInteger W = new BigInteger(sc.next()); BigInteger N = new BigInteger(sc.next()); BigInteger K = new BigInteger(sc.next()); System.out.println((H.multiply(W).mod(N.add(BigInteger.ONE)).compareTo(K) == 0)? "YES" : "NO"); } }