#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    int min_price, drop_off, money, init_price;
    cin >> init_price >> drop_off >> min_price >> money;
    int curr_price = init_price;
    int bought = 0;
    while(money - curr_price > 0 && curr_price != min_price) {
        //cout << "money:" << money << '\n';
        money = max(money-curr_price, 0);
        bought++;
        curr_price = max(min_price, curr_price-drop_off);
        //cout << "curr_price: " << curr_price << '\n';
    }
    bought += (money/curr_price);
    cout << bought;
    return 0;
}