#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define mp make_pair
#define F first
#define S second
#define sz(x) (int)x.size()
#define all(x) (x).begin(), (x).end()
#define Red ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define rep(i, n) for(int i =0 ; i < n; ++i)
#define Rep(i,a,b) for(int i=a;i<=b;i++)
#define pii pair < int, int >
typedef vector<int> vi;
typedef  long long ll;
const int mod =1e9+7;
const int N = (int)2e5 + 5;

void solve(){
      int a,b,c,d;
      cin>>a>>b>>c>>d;
      for(int i=0;;i++){
      	if(i%2==0)c-=b;
      	else a-=d;
      	if(a<=0){
      		cout<<"No";
      		return;
      	}
      	if(c<=0){
      		cout<<"Yes";
      		return;
      	}
      }
}

int main(){
	Red;
	int t=1;
	//cin>>t;
	while(t--)
	solve();
	return 0;
}