#include<bits/stdc++.h>
using namespace std;
using i64 = int_fast64_t;
#define rep(i, N) for(i64 i = 0; i < N; i++)
#define Rep(i, k, N) for(i64 i = k; i < N; i++)
#define all(v) v.begin(), v.end()
#define eb emplace_back
#define Cout(s) cout << s << endl
string Yes(bool b) {if(b){return "Yes";} else {return "No";}}
string YES(bool b) {if(b){return "YES";} else {return "NO";}}

int main(){
    int A, B, C, D;
    cin >> A >> B >> C >> D;
    Cout(Yes((C+B-1)/B <= (A+D-1)/D));
}
