I need help understanding the issue with this nested if else

Question

I'm trying to write a simple program to differentiate even and odd numbers and apply a function to them based upon their values, I try to run this and I get an "else without previous if" on both of my "else" statements

I submitted this to my class help forum and they said to include my if statements with brackets, which I have done. (possibly incorrectly)

int output = 0;
if (Input < 0); 
{
    cout << "0" << endl:
} else 
{
    if (Input % 2 == 0);
    {
        output = (Input / 2);
        cout << output << endl;
    }
}
else 
{   if (output = (3 * Input) + 1);
    {
        cout << output << endl;
    }
}

Here is the error:

error: ‘else’ without a previous ‘if’ on both of the else statements

Answer 1

If you align your indentation properly, the problem becomes clear.

if (Input < 0)
{
    cout << "0" << endl:
}
else 
{
    if (Input % 2 == 0)
    {
        output = (Input / 2);
        cout << output << endl;
    }
}
else 
{
    if (output = (3 * Input) + 1)
    {
        cout << output << endl;
    }
}

There are two else in succession. It makes no sense.

Also, you are not supposed to close if () statements with ; , if you do that you are effectively telling the compiler that this if () doesn't trigger anything (it's been closed with no code associated to it).