int DaysInMonth(int m, int y)
// pre: 1 <= m <= 12 (1 = Jan, 2 = Feb, etc.)
//	    y >= 0
// post: return numbers of day in month
{
	switch (m)
	{
		case 1:
		case 3:
		case 5:
		case 7:
		case 8:
		case 10:
		case 12: return 31;
		case 4:
		case 6:
		case 9:
		case 11: return 30;
		case 2: if (LeapYear(y))
					return 29;
				else
					return 28;
		default: return -1;
	}
}

bool LeapYear(int y)
// pre: y >= 0
// post: returns true if y is a leap year
{
	if (y % 400 == 0)
		return true;
	else if (y % 100 == 0)
		return false;
	else if (y % 4 == 0)
		return true;
	return false;
}

int ToInt(const apstring & s)
// pre: string s contains only digits
// post: returns integer value of string s
{
	int value = 0;
	for (int i = 0; i < s.length(); i++)
	{
		value *= 10;
		value += s[i] - '0';
	}
	return value;
}