#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) 
{ int c=0;
    while(s>m&&s>0)
    {s=s-p;
    p=p-d;
    c++;
    }
        return(c);
}

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;
}