#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) {
    int ans = 0;
    int spent = 0;
    for(int i = p;spent<=s && (s - spent) >= i; ){
        ans++;
        spent += i;
        if (i - d <= m) i = m;
        else i = i - d;
    }
    return ans;
}

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;
}