#include <bits/stdc++.h>
#ifdef _DEBUG
#include "debug.hpp"
#else
#define debug(...)
#endif
#define REP(i, m, n) for(int i = (int)(m); i < (int)(n); ++i)
#define rep(i, n) REP(i, 0, n)
#define rrep(i, n) for(int i = (int)(n)-1; i >= 0; --i)
#define whole(x) (x).begin(), (x).end()
#define fi first
#define se second
#define int long long
using namespace std;
using ll = long long;
using P = pair<int, int>;
using ld = long double;
constexpr int INF = 1LL<<60;
constexpr long long LINF = 1LL<<60;
template<class T, class U> inline bool chmax(T &a, const U &b) { if(a < b) { a = b; return true; } return false; }
template<class T, class U> inline bool chmin(T &a, const U &b) { if(a > b) { a = b; return true; } return false; }

int l, r, m, k;

signed main() {
  cin.tie(0); ios::sync_with_stdio(false);
  cin >> l >> r >> m >> k;
  l *= k;
  r *= k;
  int t = l/m;
  if(t*m == l || (t+1)*m <= r) cout << "Yes" << '\n';
  else cout << "No" << '\n';
  return 0;
}