#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 cnt = 0;
    while(s-p>=0)
    {
            s = s-p;    
        
        
        if(p-d>=m)
        {
            p = p -d;    
        }
        else
        {
            p=m;
        }
        cnt++;
    }
    return cnt;
}

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;
}