#include <algorithm>
#include <cmath>
#include <iostream>
#include <string>
#include <vector>

uint32_t div_ceil(uint32_t a, uint32_t b) {
  return (a % b == 0) ? a / b : a / b + 1;
}

int main() {
  uint32_t T_HP = 0, T_ATT = 0, A_HP = 0, A_ATT = 0;
  std::cin >> T_HP >> T_ATT >> A_HP >> A_ATT;

  std::cout << (div_ceil(T_HP, A_ATT) >= div_ceil(A_HP, T_ATT) ? "Yes" : "No")
            << std::endl;

  return 0;
}