#define _GLIBCXX_DEBUG
#define ll long long
#include <bits/stdc++.h>
using namespace std;
using Graph = vector<vector<int>>;

int main(){
  ll H, W; cin >> H >> W;
  ll HW = H*W;
  ll N, K; cin >> N >> K;
  ll mod = HW%N;
  if(mod == 0) mod = N;
  if(mod == K) cout << "YES" << endl;
  else cout << "NO" << endl;
}