#include <iostream>

int main(void){
    std::cin.tie(nullptr); std::cin.sync_with_stdio(false); std::cout.tie(nullptr);
    int L, R, M, K; std::cin >> L >> R >> M >> K;
    const long long int X = (long long int)(L) * K, Y = (long long int)(R) * K;
    long long int P = (X / M) * M; if(P < X) P += M;
    std::cout << ((P > Y) ? "No" : "Yes") << '\n';
    return 0;
}