#include <bits/stdc++.h>
using namespace std;
 
int main(){
    int V, T, S, D;
    cin >> V >> T >> S >> D ;
    if (V*T <= D && D <= V*S)cout << "No" << endl;
    else cout << "Yes" << endl;
}
#include<bits/stdc++.h>
using namespace std;
const int N=1e3+15;
typedef long long ll;
string s;
int main()
{
    ll a,b,c,d;
    cin>>a>>b>>c>>d;
    if(a==c&&b==d)
    {
        cout<<"0"<<endl;
        return 0;
    }
    if(a+b==c+d)
    {
        cout<<"1"<<endl;
        return 0;
    }
    if(a-b==c-d)
    {
        cout<<"1"<<endl;
        return 0;
    }
    if(abs(a-c)+abs(b-d)<=3)
    {
        cout<<"1"<<endl;
        return 0;
    }
    if( abs(a+b) %2== abs(c+d)%2)
    {
        cout<<"2"<<endl;
        return 0;
    }
    if(c>=a)
    {
        ll lb=b+(c-a);
        if(abs(lb-d)<=3)
        {
            cout<<"2"<<endl;
            return 0;
        }
        
        lb=b-(c-a);
        if(abs(lb-d)<=3)
        {
            cout<<"2"<<endl;
            return 0;
        }
    }
    if(c<a)
    {
        ll lb=b-(a-c);
        if(abs(lb-d)<=3)
        {
            cout<<"2"<<endl;
            return 0;
        }
        
        lb=b+(a-c);
        if(abs(lb-d)<=3)
        {
            cout<<"2"<<endl;
            return 0;
        }
    }
    cout<<"3"<<endl;
    return 0;
}
