#include <bits/stdc++.h>

using namespace std;

void howManyGames(int p, int d, int m, int s) {
    int count=1,dummy=m;
    
        while(m>1)
        {
            p=p-d;
            if(p<dummy)
                p=m;
            s=s-p;
            if(s<=0)
                break;
            m--;
            count++;
        }

    
    cout<<count<<endl;
    // Return the number of games you can buy
}

int main() {
    int p;
    int d;
    int m;
    int s;
    cin >> p >> d >> m >> s;
    howManyGames(p, d, m, s);
  
    return 0;
}