#include <bits/stdc++.h>

using namespace std;

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

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;
}