#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) {
    int n=floor((p-m)/d)+1;
    int c=0;
    while(s>0)
    {
        if(c<n)
            s=s-(p-(c)*d);
        else
            s=s-m;
        c++;            
    }
    if(s<0)
        c--;
    return c;
}

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;
}