#include <bits/stdc++.h>

using namespace std;

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