CS50 Vigenere expected output, not a prompt for input

Question

when I check my program, there is the "expected output, not a prompt for input" error for every input they are trying to check. however, when I am testing it, all inputs seem to be exactly the same as the output the check requires. Here is the code:

int main(int argc, string argv[])
{
    if (argc!=2)
    {
        printf("Please, enter one keyword.\n");
        return 1;
    }
    string Key = argv[1];
    int KeyLen = strlen(Key);
    for (int i=0; i<KeyLen;i++)
    {
        if (isalpha(Key[i]))
        {
            Key[i]=tolower(Key[i]);
        }
        else
        {
            printf("The key should not contain non-alphabetic characters.\n");
            return 1;
        }
    }
    string UserInput = GetString();
    int InputLen= strlen(UserInput);
    int KeyCount = 0;
    int j;
    for (j=0; j<InputLen; j++)
    {
        if (isalpha(UserInput[j]))
        {
            if(islower(UserInput[j]))
            {
                printf("%c", ((((UserInput[j]-97)+(Key[KeyCount]-97))%26)+97));
                if(KeyCount<KeyLen-1)
                {
                    if(KeyLen>1)
                    {
                        KeyCount++;
                    }
                }
                else
                {
                    KeyCount=0;
                }
            }
            if(isupper(UserInput[j]))
            {
                printf("%c", ((((UserInput[j]-65)+(Key[KeyCount]-97))%26)+65));
                if(KeyCount<KeyLen-1)
                {
                    if(KeyLen>1)
                    {
                        KeyCount++;
                    }
                }
                else
                {
                    KeyCount=0;
                }
            }
        }
        else
        {
            printf("%c", (UserInput[j]));
        }
    }
    printf("\n");
    return 0;
}

What am I doing wrong? Thank you in advance!!!

Answer 1

Current incarnation of the problem requires some additional output:

• Otherwise, your program must proceed to prompt the user for a string of plaintext, p, (as by a prompt for plaintext:) which it must then encrypt according to Vigenère’s cipher with k, ultimately printing the result (prepended with ciphertext:) and exiting, with main returning 0.

(source)