#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 temp = 1,count =0;
    count = count + p;

    while(p>= m && count <= s)
    {
        p = p-d;
        count = count + p;
        temp++;
    }
    return temp;
}

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;
}