#include<iostream>

int main()
{
    int n, m, p, q;
    std::cin >> n >> m >> p >> q;
    
    int month = 0;
    int count = 0;
    while(n > 0)
    {
        n -= (((month + 1) >= p) && ((month + 1) < p + q))? (m + m):m;
        
        month++;
        count++;
        
        month %= 12;
    }
    
    std::cout << count << std::endl;
    return 0;
}