#include <bits/stdc++.h>

using namespace std;
//s total money , p intial cost, d dollars less and untill m reached
int howManyGames(int p, int d, int m, int s) {
    int games = 0, i = 0;
    while(p >= m && s >= p)
    {
        games++;
        s = s - p;
        p = p - d;
    }
    if(s >= p)
    {
        games = games + (s / m);
    }
    return games;
}

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;
}