#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) {
    int ans=0,i=p;int game=1;
    while(i>m)
    {
        if(p>m)
        {
            p=p-d;
            
            ans=ans+p;
            if(ans<s)
            {
                 game++;
            }
       
        }
        i--;
        
    }
    // Return the number of games you can buy
    return game;
}

int main() {
    int p;
    int d;
    int m;
    int s;
    cin >> p >> d >> m >> s;
    int answer = howManyGames(p, d, m, s);
    cout << answer << endl;
    return 0;
}