#include <bits/stdc++.h>
using namespace std;
#define int long long 
#define alpha_size 26


int32_t main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr); cout.tie(nullptr);    
    
    int a, b, c, d;
    cin >> a >> b >> c >> d;
    
    int cnt = 1;
    bool takahashi = false, aoki = false;
    while (!takahashi && !aoki){
      if (cnt & 1) 
        c -= b;
      else
        a -= d;
      if (a <= 0){
        aoki = true;
        break;
      }
      if (c <= 0){
        takahashi = true;
        break;
      }
      cnt++;
    }
    if (takahashi)
      cout << "Yes" << endl;
    else
      cout << "No" << endl;
}
