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

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