#include <iostream>

using namespace std;

int main()
{
    int p,d,m,s;
    cin >> p >> d >> m >> s;

    int output = 0;
    while (true) {
        s -= p;
        p = max(p-d,m);
        if (s >= 0)
            output++;
        else
            break;
    }
    cout << output;
}