#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(int argc, char *argv[])
{
    int length;
    length = strlen(argv[1]);

    int i;
    int digit;
    int c;
    c = 0;

    for (i=0; i<length; i++)
    {
        digit = argv[1][i] - '0';
        if (digit != 0)
        {
            c += digit;
            if (c > 10)
            {
                c -= 9;
            }
        }
    }
    printf("Checksum is: %d\n", c);

    return(0);
}