#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) {
    int cnt=0;
    if(s<p)
        return 0;
    else
    {
        ++cnt;
        s-=p;
        p-=d;
        if(p<m)
            p=m;
        while(s>=p)
        {
           ++cnt;
            s-=p;
           if(p!=m)
           {
               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;
}