#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

int main() {
    ll L, R, M, K;
    cin >> L >> R >> M >> K;

    ll n = (L * K + M - 1) / M;
    if (n * M <= R * K) {
        cout << "Yes" << endl;
    } else {
        cout << "No" << endl;
    }

    return 0;
}