#include <iostream>
using namespace std;

void read_and_write()
{
	int k, m, d,s=1, books=0;
	cin >> k >> m >> d;
	int kdays = d;
	if (d < 6)
		books = k + m-s;
	else
		books = m-s;
	while (books >= 0)
	{
		kdays++;
		s++;
		if (kdays%8 < 6)
			books = k + books-s;
		else
			books = books - s;
	}
	cout << kdays - d<< endl;
}
int main()
{
	read_and_write();
	system("pause");
	return 0;
}