#include<bits/stdc++.h>
#include <algorithm>
using namespace std;

#define ll long long int 
#define MOD 1000000007
#define sc(a) scanf("%lld",&a)
#define f0(n) for(ll i=0;i<n;i++)
#define f1(n) for(ll i=1;i<=n;i++)
#define pb(v,a) v.push_back(a)
#define pbp(v,a,i) v.push_back(make_pair(a,i)) 
#define srt(v) sort(v.begin(),v.end());

int n,a[300001];

int main()
{
	ll a,b,c,d;
	cin>>a>>b>>c>>d;
	for(ll i=1;i<=i;i++)
	{
		if(i%2==1)
		{
			c=c-b;
			if(c<=0)
			{
				cout<<"Yes"<<endl;
				break;
			}
		}
		else
		{
			a=a-d;
			if(a<=0)
			{
				cout<<"No"<<endl;
				break;
			}
		}

	}
}