#include <stdio.h>
#include <cs50.h>
#include <string.h>
#include <ctype.h> //alpha/digit functions
#include <stdlib.h> //for atoi function

int main(int argc, string argv[]) //where argc is count of arguments e.g. ./caesar 3 --> argc = 2, and string argv lists the args, e.g. argv[0] = ./caesar and argv[1] = 3
{
        //Checks argc, the count of arguments. There should be 2, ./caesar and a key.
        if (argc != 2)
        {
            printf ("Usage: %s key\n", argv[0]);
            return 1;
        }

    int k = atoi (argv[1]);

    for (int i = 0; i < strlen(argv[1]); i++) //Runs through whole argv[1] string to check if it's acceptable
    {
        if (isdigit(argv[1][i]) == false || k < 0)
        {
            printf ("Usage: %s key\n", argv[0]);
            return 0;
        }

        else //the string consists solely of digits, convert to int
        {

            printf ("Success! Your key is %i\n", k);
            return 0;
        }

    }

}