#include <bits/stdc++.h>
#define rep(i, a, n) for (int i = a; i < n; i++)
#define repr(i, a, n) for (int i = n - 1; i >= a; i--)
using namespace std;
using ll = long long;
using P = pair<int, int>;
template <typename T> void chmin(T &a, T b) { a = min(a, b); }
template <typename T> void chmax(T &a, T b) { a = max(a, b); }

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);

  int l, r, m, k;
  cin >> l >> r >> m >> k;
  if (k == 0) {
    cout << "Yes" << endl;
    return 0;
  }

  int x = m / k;
  if (m % k)
    x++;
  if (x >= l && x <= r)
    cout << "Yes" << endl;
  else
    cout << "No" << endl;
}