#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define int long long
#define mp make_pair
#define endl "\n"
#define pii pair<int,int> 
#define ff first
#define ss second
#define mii map<int,int>
#define si set<int>
#define sti stack<int>
#define qi queue<int>
#define vi vector<int>
#define pq priority_queue<int>
#define IOS ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
const int M=1e9+7;

int32_t main(){
    IOS;
    int a,b,c,d;
    cin>>a>>b>>c>>d;
    int cur=0;
    while(a>0&&c>0){
        if(cur==1){
            a-=d;
            cur=0;
        }
        else{
            c-=b;
            cur=1;
        }
    }
    if(cur) cout<<"Yes";
    else cout<<"No";
}
