#include <bits/stdc++.h>
using namespace std;

int main()
{
    int n,m,p,q;
    cin >> n >> m >> p >> q;

    int ans = 0;
    while(n > 0){
        int month = ans % 12 + 1;
        if(month >= p && month < p + q) n -= 2 * m;
        else n -= m;
        ans++;
    }

    cout << ans << endl;

    return 0;
}