#include <iostream>

int main(){
  long long h, w, n, k;
  int mod;
  std::cin >> h >> w >> n >> k;

  h *= w;
  mod = h % n;

  if((k == n && h == 0) || (k == h)){
    std::cout << "YES" << std::endl;
  }
  else{
    std::cout << "NO" << std::endl;
  }

}