#include <bits/stdc++.h>

using namespace std;

void howManyGames2(int p, int d, int m, int s) {
    // Return the number of games you can buy
    int count = 1;
    s = s - p;
    int check = (p-m)/d;
    int intm = p*check - d*(check*(check+1))/2;
        
}
int howManyGames(int p, int d, int m, int s) {
    // Return the number of games you can buy
    int count = 0;
    if(s < p)
            return 0;
    count++;
    s=s-p;
   // cout<<p<<" ";
    while((p-count*d)>m && s>0)
    {
        //cout<<p-(count)*d<<" ";
        s = s - p + (count)*d;
        count++;
        //cout<<p-(count)*d<<" ";
    }
    if(s<0)
        return count-1;
    //s = s + p - (count-1)*d;
    while(s>0)
    {
       // cout<<m<<" ";
        s = s - m;
        count++;
        
    }
    if(s!=0)
        count--;
    return count;
        
}
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;
}