#include"bits/stdc++.h"

#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define REP(i, n) for (int i = 1; i < (int)(n); i++)
#define all(v) v.begin(), v.end()
using ll = long long;

using namespace std;
int main(){
	int a, b, c, d;
	int cnt = 0;
	cin >> a >> b >> c >> d;
	while(a >= 1 && c >= 1){
		if(cnt % 2 == 1)a -= d;
		if(cnt % 2 == 0)c -= b;
		cnt++;
	}

	if (a >= 1) {
		cout << "Yes" << endl;
	}
	else {
		cout << "No" << endl;
	}
}
