#include <bits/stdc++.h>
using namespace std;
/* typedef */
typedef long long ll;
typedef pair<int, int> pii;
/* constant */
const int INF = 1 << 30;
const ll LINF = 1LL << 50;
const int NIL = -1;
const int MAX = 10000;
const int mod = 1000000007;
const double pi = 3.141592653589;
/* global variables */
/* function */
/* main */
int main(){
    int a, b, c, d;
    cin >> a >> b >> c >> d;
    for (int i = 0; i < 500; i++) {
        if (i % 2 == 0) {
            c -= b;
            if (c <= 0) {
                cout << "Yes" << '\n';
                return 0;
            }
        }
        else {
            a -= d;
            if (a <= 0) {
                cout << "No" << '\n';
                return 0;
            }
        }
    }
}
