#include <bits/stdc++.h>
#define rep(i,n) for(int i=(0);i<(n);i++)

using namespace std;

typedef long long ll;
typedef long double ld;

template<class T> bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T> bool chmin(T &a, const T &b) { if (a>b) { a=b; return 1; } return 0; }

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

	ll l, r, m, k;
	cin >> l >> r >> m >> k;

	ll lk = l * k, rk = r * k;
	if(lk == 0){
		cout << "Yes" << endl;
		exit(0);
	}

	if((lk - 1) / m != rk / m){
		cout << "Yes" << endl;
	}else{
		cout << "No" << endl;
	}

}