#include <cstdio>
#include <iostream>
#include <string>
#include <sstream>
#include <stack>
#include <algorithm>
#include <cmath>
#include <queue>
#include <map>
#include <set>
#include <cstdlib>
#include <bitset>
#include <tuple>
#include <assert.h>
#include <deque>
#include <bitset>
#include <iomanip>
#include <limits>
#include <chrono>
#include <random>
#include <array>
#include <unordered_map>
#include <functional>
#include <complex>
#include <numeric>

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

constexpr long long MAX = 5100000;
constexpr long long INF = 1LL << 60;
constexpr int inf = 1000000007;
//constexpr long long mod = 1000000007LL;
constexpr long long mod = 998244353LL;

using namespace std;
typedef unsigned long long ull;
typedef long long ll;

void print(bool ok) {
	if (ok) puts("Yes");
	else puts("No");
	exit(0);
}


int main()
{
	/*
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
    */

	ll L, R, M, K; cin >> L >> R >> M >> K;
	ll left = L * K;
	ll right = R * K;
	if (left == 0) {
		if (right >= M)print(true);
	}else{
		if (right / M != (left - 1) / M) print(true);
	}
	print(false);
	return 0;
}