#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef vector<int> pi;
typedef pair<int,int> vi;

#define F first
#define S second
#define PB push_back
#define MK make_pair
#define REP(i, a, b) for (int i=a; i < b; i++)


bool sort_by(vi c, vi d){
	return c.S < d.S;
}

int main() {
	int a, b, c, d;
	cin >> a >> b >> c >> d;
	int i = 0;
	while(a > 0 && c > 0){
		if(i%2 == 0) c-= b;
		else a -= d;
		++i;
	}
	
	cout << (a>0?"Yes":"No");

}
