#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>

int main() {
    
    int originalPrice;
    int decrease;
    int lowestPrice;
    int bank;
    std::cin >> originalPrice >> decrease >> lowestPrice >> bank;
    
    int countGames = 0;
    int currentMoney = bank;
    int currentPrice = originalPrice;
    
    while (currentMoney >= currentPrice)
    {
        ++countGames;
        currentMoney = currentMoney - currentPrice;
        //std::cout << currentPrice << " ";
        if (currentPrice - decrease > lowestPrice)
        {
            currentPrice = currentPrice - decrease;
        }
        else
        {
            currentPrice = lowestPrice;
        }
    }
    
    std::cout << countGames;
    
    return 0;
}