/*
Function decrypts a cipher with key n. (Flips the word before.)
input: string cipher, int n.
output: none.
*/
void decrypt(char* cipher, int n)
{
    int i = 0;
    char newStr[SIZE] = { 0 };

    while (*(cipher + i) != '\0')
    {
        // This line is crazy... It gets the i left most char removes 'a' from it adds the key n and module it by 26 and returns the 'a'.
        *(newStr + i) = 'a' + ((*((cipher + (strlen(cipher) - 1)) - i) - 'a' + n) % ABC_SIZE);
        i++;
    }
    strcpy(cipher, newStr);
}