#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
using namespace std;
using ll = long long;
using P = pair<int,int>;

int A,B,C,D;

int main() {
  cin >> A >> B >> C >> D;
  bool canWin = false;
  rep(i, 200){
    int ret;
    if(i%2 == 0){
      C = C - B;
      if(C <= 0){
        canWin = true;
        break;
      }
    } else {
      A = A - D;
      if(A <= 0){
        canWin = false;
        break;
      }
    }
  }
  if(canWin) cout << "Yes" << endl;
  else cout << "No" << endl;
}
