#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <map>
#include <cmath>
#include <set>
#include <queue>
using namespace std;
#define ll long long
#define rep(i, n) for(int i = 0; i < n; i++)

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