#include <bits/stdc++.h>

int64_t f(int64_t n, int64_t m){
  if(n < 0){
    return 0;
  }else{
    return n / m + 1;
  }
}

int main(){
  int64_t L, R, M, K; std::cin >> L >> R >> M >> K;

  int64_t min_v = L * K;
  int64_t max_v = R * K;


  bool ans = f(max_v, M) - f(min_v-1, M) > 0;

  std::cout << (ans ? "Yes" : "No") << "\n";
  
  return 0;
}