HOJ 2892 YY, and YY again

http://acm.hit.edu.cn/hoj/problem/view?id=2892

#include <stdio.h>#include <string.h>int main(){    int len, i, sum;    char str[256];    while(gets(str))    {        sum = 0;        len = strlen(str);        for (i = 0; i < len; i++)        {            if ( ! ( (str[i] >= 'A') && (str[i] <= 'Z') ) )            {                str[i] = 0;            }            else            {                str[i] = str[i] - 'A' + 1;            }            sum+=str[i];        }        if (sum > 100)            printf("INVALID\n");        else            printf("%d\n", sum);    }    return 0;}