#include <stdio.h>
#include <math.h>
#include <cs50.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>

const int A = 26;

int main(int argc, string argv[])
{
    //checking if one command-line argument is given
    if (argc != 2)
    {
        printf("Usage: ./caesar key\n");
        return 1;
    }
    
    else 
    {
        //testing if key consists of proper positive integers
        for (int i = 0, n = strlen(argv[1]); i < n ;i++)
        {
            if (isdigit(argv[1][i]) == 0)
            {
                return 1;
            }
        
        }

    }
    
    string message = get_string("plaintext: "); 
    int key = atoi(argv[1]);
    printf("ciphertext: ");
    for (int i = 0, n = strlen(message); i < n; i++)
    {
        string c;
        printf("%c", message[i] + key);
    }
printf("\n");    
}