#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) {
    // Return the number of games you can buy
    int i=0,curr=p;
    if(s < p)
        return 0;
    while(1){
        //cout<<s<<endl;
        if(i == 0){
            s = s-p;
            i++;
        }
        else{
            if(s >= curr){
                s -= curr;
                i++;
            }
            else
                break;
        }
        if(d != -1)
        curr -=d;
        if(curr <= m){
            curr = m;
            d = -1;
        }
    }
    return i;
}

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;
}