#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,j,k,l,c;
    c = p;
    j = 0;
    while(s >= k)
    {
        j++;
        k = k + c;
        c = c - d;
        if(c <= m)
        {
            c = m;
        }
    }
    return j-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;
}