#include <iostream>
#include <iomanip>
#include <vector>
#include <string>
#include <algorithm>
#include <random>
#include <cstdio>
#include <cmath>
#include <climits>
#include <queue>
#include <map>
using namespace std;
typedef long long ll;
#define rep(i, n) for(int i = 0; i < (int) n; i++)
#define rep1(i, n) for(int i = 1; i <= (int) n; i++)
#define all(v) v.begin(),v.end()

int main() {
    int a,b,c,d;
    cin >> a >> b >> c >> d;
    if (a / d < c / b) {
        cout << "Yes\n";
    } else {
        cout << "No\n";
    }
    return 0;
}