#include <iostream>

using lint = long long;

void solve() {
    lint l, r, m, k;
    std::cin >> l >> r >> m >> k;
    l *= k, r *= k;
    std::cout << (l == 0 || (l - 1) / m < r / m ? "Yes" : "No") << std::endl;
}

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

    solve();

    return 0;
}