int tolower(int c)
{
	if ((c >= 'A') && (c <= 'Z'))
		return c + ('a' - 'A');
	return c;
}

int htoi(char s[])
{
	int i;
	int n = 0;
	if (s[0] == '0' && (s[1]=='x' || s[1]=='X'))
	{
		i = 2;
	}
	else
	{
		i = 0;
	}
	for (; (s[i] >= '0' && s[i] <= '9') || (s[i] >= 'a' && s[i] <= 'f') || (s[i] >='A' && s[i] <= 'F');++i)
	{
		if (tolower(s[i]) > '9')
		{
			n = 16 * n + (10 + tolower(s[i]) - 'a');
		}
		else
		{
			n = 16 * n + (tolower(s[i]) - '0');
		}
	}
	return n;
}