#include <bits/stdc++.h>
using namespace std;

int main() {
  int A,B,C,D;
  cin >> A >> B >> C >> D;
  int cnt = 0;
  int sw = 0;
  while (sw == 0) {
    // 
    if (cnt % 2 > 0) {
      A = A - D;
    	if (A <=0) {
    	  sw = 1;
    	}
    } else {
      C = C - B;
    	if (C <=0) {
    	  sw = 1;
    	}
    }
    cnt++;
  }
  if (A > C) {
    // 
    cout << "Yes" << endl;
  } else {
  	cout << "No" << endl;
  }
}