#include <bits/stdc++.h>

using namespace std;

int main() {
    int p, d, m, s;
    cin >> p >> d >> m >> s;
    int cur = p, ans = 0;
    while (s > 0) {
        if (s >= cur)
            ++ans;
        s -= cur;
        cur = max(cur - d, m);
    }
    cout << ans << endl;
    return 0;
}