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


int main() {
    int purchases = 0;
    int wallet;
    int price;
    int discount;
    int minprice;
    
    std::cin >> price >> discount >> minprice >> wallet;
    
    while(price <= wallet)
    {
        purchases++;
        wallet = wallet - price;
        //price = std::max(price, minprice);
        if(price > minprice)
        {
            price = std::max(price - discount, minprice);
        }
    }
    
    std::cout << purchases;
    
    return 0;
}