int weekday(int year, int month, int day)
{
    int c;

    if (month < 3) {
	year -= 1;
	month += 10;
    } else {
	month -= 2;
    }

    c = year / 100;
    year = year % 100;

    return ((26 * month - 2) / 10 + day + year + year / 4 + c / 4 - 2 * c + 7777) % 7;
}