#include<bits/stdc++.h>
#define rep(i,b) for(int i=1;i<=b;i++)
#define drep(i,b) for(int i=b;i>=1;i--)
#define Rep(i,a,b) for(int i=a;i<=b;i++)
#define endl '\n'
#define int long long
#define ls i<<1
#define rs i<<1|1
#define mid (l+r)/2

using namespace std;

const int N=1e5+7;
const int mod=998244353;
int n,m,k,t,x,y,z;
int dis[N],vis[N],cnt[N];

#define pr pair<int,int>
#define ff first
#define ss second

void solve(int sum=0){
    cin>>n>>m>>x>>y;
    int t=x/m,t2=n/y;
    if(x%m) t++;
    if(n%y) t2++;
    if(t<=t2) cout<<"Yes"<<endl;
    else cout<<"No"<<endl;
}

#undef int
int main(){
    ios::sync_with_stdio(false);
    //int T;cin>>T;
    //while(T--)
    solve();
}
