#include <cs50.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
int main(int argc, string argv[])
{

    if(argc == 2)
    {
        for(int i = 0; i < strlen(argv[1]); i++)
        {
            if(!isdigit(argv[1][i]))
            {
                printf("Usage: ./caesar key");
                return 0 ;
            }
        }
        string pi = get_string("paintext: ");
        int size = strlen(pi);
        int k = atoi(argv[1]);
        char ci[size+1];
        ci[size] = '\0';
        for(int j = 0; j < size; j++)
        {
            ci[j] = (pi[j] + k) % 26;
        }
        printf("cliphertext: %s\n", ci);


    }
    else
    {
        printf("Usage: ./caesar key");
    }
}