#include <bits/stdc++.h>

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int64_t L, R, M, K;
  cin >> L >> R >> M >> K;
  int64_t x = L * K, y = R * K;
  int64_t a = x / M;
  int64_t b = y / M;
  if (x % M == 0 || y % M == 0 || a != b) {
    cout << "Yes" << '\n';
  } else {
    cout << "No" << '\n';
  }
  return 0;
}