#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)
    {
        if(p<=m)
        {
            cnt+=(s/m);
            s=s%m;
        }
        else
        {
            cnt++;
            s=s-p;
            p=p-d;
            if(p<m)  p=m;
        }
    }  
    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;
}