oppgave.c

int stringsum(char* str)
{
	int sum = 0;
	char c;
	int i;
	for (i = 0; (c = str[i]); ++i)
	{
		if (c >= 'A' && c <= 'Z')
			sum += c - 'A' + 1;
		else if (c >= 'a' && c <= 'z')
			sum += c - 'a' + 1;
		else
			return -1;
	}

	return sum;
}