#include <iostream>
#include <string>
using namespace std;

int main(){
    int V, T, S, D;
    cin >> V >> T >> S >> D;
    if (D >= V * T && D <= V * S) {
        cout << "No";
    } else {
        cout << "Yes";
    }
    return 0;
}
#include <bits/stdc++.h>

using namespace std;

#define ull unsigned long long

void solve()
{
    vector<int> v(3);
    cin >> v[0] >> v[1] >> v[2];
    sort(v.begin(),v.end());
    if(v[2]-v[1] == v[1]-v[0])
        cout << "Yes" << endl;
    else
        cout << "No" << endl;
    return;
}

int main()
{
    ios_base::sync_with_stdio(false); 
    cin.tie(NULL);
    int t = 1;
    //cin >> t;
    while(t--) 
        solve();
    return 0;
}