        #include <bits/stdc++.h>
        using namespace std;
        #define int long long int
        #define pb push_back
        #define mk make_pair
        #define ft first
        #define sc second
        #define ppb pop_back
        #define sz size
        #define forn(i,a,n) for(i=a;i<n;i++)
        #define M 998244353 
        #define inf 2e18

        bool compare(pair<int,int> a,pair<int,int> b){
            if(a.first==b.first)
                return a.second<b.second;
            return a.first<b.first;
        }

        signed main() {
 
        ios_base::sync_with_stdio(false);
        cin.tie(NULL);
        cout.tie(NULL);
        
        int a,b,c,d;
        cin>>a>>b>>c>>d;
        int fl=0;
        while(a>0&&c>0){
            if(fl)
            a=max(0ll,a-d);
            else
            c=max(0ll,c-b);
            // cout<<b<<" ";
            // cout<<a<<" "<<c<<"\n";
            fl=!fl;
        }
        // cout<<a<<" "<<c;
        if(a==0)
            cout<<"No\n";
        else
            cout<<"Yes\n";

        return 0;
    }