Discussion on: Daily Challenge #110 - Love VS. Friendship

#include <stdio.h>

int main(int argc, char *argv[]) 
{
    if (argc != 2)
    {
        printf("Usage: ./strength string\n");
        return 1;
    }
    int sum = 0;
    char *c = argv[1];
    while(*c != '\0')
    {
        if (*c < 'a' || *c > 'z')
        {
            printf("Invalid argument\n");
            return 1;
        }
        sum += *c - 'a' + 1;
        c++;
    }
    printf("%i\n", sum);
    return 0;
}