#include <vector>
#include <string>
#include <iostream>
#include <queue>
#include <algorithm>
#include <functional>
#include <map>
#include <array>
#include <cmath>
#include <set>

long long PRIME = 1e9 + 7;
long long PRIME2 = 998244353;

using namespace std;


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

    int turn_T = ceil((double)C / B);
    int turn_A = ceil((double)A / D);

    if(turn_T <= turn_A){
        cout << "Yes";
    }
    else{
        cout << "No";
    }
}

