#include <bits/stdc++.h>

using namespace std;

using ll = long long;

constexpr char newl = '\n';

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    ll l, r, m, k;
    cin >> l >> r >> m >> k;

    ll minv = l * k;
    ll maxv = r * k;

    bool ans = false;
    if (maxv - minv + 1 >= m) ans = true;
    
    minv %= m;
    maxv %= m;

    if (minv > maxv || minv == 0) ans = true;

    cout << (ans ? "Yes" : "No") << newl;
    return 0;
}