#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) {
    int i;
        for( i=0;p>=m && s>=0;i++)
        {
            s=s-p;
            p=p-d;
            
        }
        
        p=p+d;
        while(s>=0)
        {
            s=s-m;
            i++;
        }
    return i-1;
}

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;
}