#include <vector>
#include <iostream>
#include <algorithm>

int main()
{
    auto p = 0;
    auto d = 0;
    auto m = 0;
    auto s = 0;
    std::cin >> p >> d >> m >> s;
    
    auto sum = 0;
    auto currentCost = p;
    auto count = 0;
    
    while(sum <= s)
    {
        sum += currentCost;
        if(sum <= s) ++count;
        
        if(currentCost - d > m) currentCost -= d;
        else currentCost = m;
    }
    
    std::cout << count;
    
    return 0;
}