#include "bits/stdc++.h"
using namespace std;
 
////////////// Prewritten code follows. Look down for solution. ////////////////

#define fs first
#define sc second
#define pb push_back
#define len(x) ((int)(x).size())
#define fastio ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);

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

const ll LINF = 1e18;
const int INF = 1e9;
const int MOD = 1e9+7;

/// command for char arrays with spaces -> scanf(" %[^\n]", text);
 
////////////////////////// Solution starts below. //////////////////////////////

int main(){
	fastio;
	int a, b, c ,d;
	cin >> a >> b >> c >> d;
	int turn = 0;
	while(a > 0 and c > 0){
		turn++;
		if(turn&1) c-=b;
		else a-=d;
	}	
	if(turn&1) cout << "Yes\n";
	else cout << "No\n";
	return 0;
}