#include <vector>
#include <queue>
#include <deque>
#include <stack>
#include <algorithm>
#include <functional>
#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <cctype>
#include <string>

using namespace std;

typedef long long ll;

int main() {
  ll h, w, n, k;
  cin >> h >> w >> n >> k;
  if (h*w > n) {
    ll a = (h*w)%n;
    if ((a == 0 && k == n) ||
	a == k) {
      std::cout << "YES" << std::endl;
    }else {
      std::cout << "NO" << std::endl;
    }
  }else {
    if (k == h*w) {
      std::cout << "YES" << std::endl;
    }else {
      std::cout << "NO" << std::endl;
    }
  }
}