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

int main(){
    int H1, A1, H2, A2;
    cin >> H1 >> A1 >> H2 >> A2;
    while(true){
        H2 -= A1;
        if(H2 <= 0){
            cout << "Yes" << endl;
            break;
        }
        H1 -= A2;
        if(H1 <= 0){
            cout << "No" << endl;
            break;
        }

    }
}