#include <bits/stdc++.h>

using namespace std;

int howManyGames(int price_start, int discount, int match, int savings) {
    // Return the number of games you can buy
    int num_games = 0;
    int price_next = price_start;
    while (savings >= price_next) {
        // Purchase game
        savings -= price_next;
        num_games += 1;
        price_next -= discount;
        if (price_next < match) {
            price_next = match;
        }
    }
    return num_games;
}

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;
}