#include <bits/stdc++.h>

using namespace std;

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

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;
}