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

int main(){
    int A,B,C,D;
    cin>>A>>B>>C>>D;

    int cnt = 0;

    while(1){
        if(cnt % 2 == 0){
            C -= B;
        }else{
            A -= D; 
        }

        if(C <= 0 || A<= 0) break;
        cnt++;
    }

    if(C<=0) cout<<"Yes"<<endl;
    else cout<<"No"<<endl;
    
    return 0;
}