#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) {
    int counter = 0;
    int price = p;
    while (s >= price){
        s -= price;
        counter++;
        price -= d;
        if (price < m)
            price = m;
    }
    return counter;
}

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;
}