string key = argv[1];

for (int i = 0, k = strlen(key); i < k; i++)
{
    if (isdigit(key[i]))
    {
        printf("Please give an alphabetical keyn");
        return 1;
    }
}

string plain = GetString ();
int j = 0;
int plainn = strlen(plain);


for (int i = 0; i < plainn; i++)
{
    if (j>=(strlen(argv[1])))
    {
        j = 0;
    }

    if (islower(key[j]))
    {
        key[j] = key[j] - 97;
    }

    else if (isupper(key[j]))
    {
        key[j] = key[j] - 65;
    }

    if (isalpha(plain[i]))
    {
        if (islower(plain[i]))
        {
            printf("%c", (((( plain[i]-'a')+(key[j++]))%26)+'a'));

        }

        else
        {
            printf("%c", (((( plain[i]-'A')+(key[j++]))%26)+'A'));

        }
    }

    else
    {
        printf("%c", plain[i]);
    }
}
printf("n");