#include <bits/stdc++.h>
using namespace std;
 
int main(){
    int A, B, C, D;
    cin >> A >> B >> C >> D;
    bool E = false;
    while((A-D <= 0) || (C - B <= 0)){
        A = A - D;
        C = C - B;
    }
    if(A>0){
        E = true;
    }
    if(E == true){
        cout << "Yes" << endl;
    }
    else{
        cout << "No" << endl;
    }
}
