#include <bits/stdc++.h>

using namespace std;

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

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;
}