#include <bits/stdc++.h>
using namespace std;

int main() {
    
    int p, d, m, s;
    cin >> p >> d >> m >> s;
    int c = 0, sum = 0; p += d;
    while (1)
    {
        if (p-d <= m)
        {
            p = m;
        }
        else
        {
            p -= d;
        }
        sum += p;
        if (sum <= s)
            c++;
        else
            break;
    }//cout << endl; cout << sum << " " << p << endl;
    cout << c;
    
    return 0;
}