/* -*- coding: utf-8 -*-
 *
 * 384.cc: No.384 マス埋めゲーム2 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

/* typedef */

typedef long long ll;

/* global variables */

/* subroutines */

/* main */

int main() {
  ll h, w, n, k;
  cin >> h >> w >> n >> k;

  bool ok = ((h + w - 1) % n == k % n);
  cout << (ok ? "YES" : "NO") << endl;
  return 0;
}