#include <bits/stdc++.h>
using namespace std;
const int MOD = (int)1e9 + 7;
const int INF = 100100100;
const double PI = 3.14159265358979323846;
typedef long long ll;
#define FOR(i, a, b) for (ll i = (a); i < (b); ++i)
#define REP(i, n) for (ll i = 0; i < (n); ++i)

int main() {
  ll a, b, c, d;
  cin >> a >> b >> c >> d;
  ll turn = 0;
  while (1) {
    if (a <= 0) {
      cout << "No" << endl;
      break;
    } else if (c <= 0) {
      cout << "Yes" << endl;
      break;
    }
    turn++;
    if (turn % 2 == 1) {
      c -= b;
    } else {
      a -= d;
    }
  }
  return 0;
}