#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

inline ll floor_div(ll a, ll b) {
  return a / b - (a % b < 0);
}

int main() {
  cin.tie(nullptr)->sync_with_stdio(false);
  ll l, r, m, k;
  cin >> l >> r >> m >> k;
  ll x = l * k, y = r * k;
  if (floor_div(x - 1, m) == floor_div(y, m)) {
    cout << "No" << '\n';
  }
  else {
    cout << "Yes" << '\n';
  }
  return 0;
}