#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) 
{
    // Return the number of games you can buy
    int numOfGames = 0;
    while (s - p >= 0)
    {
        s -= p;
        if (p - d >= m)
        {
            p -= d;
        }
        else 
        {
            p = m;     
        }
        numOfGames++;
    }
    return numOfGames;
}

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;
}