What is wrong with the following function template (Other than the fact that it really does almost nothing)?

What will be an ideal response?
```
template
int f( int & x )
{
return x;
}
int main()
{
int y = 3, z;
z = f(y);
}
```

There is a rule “Every template argument specified in the template-
argument-list must be used in the argument of a function template.” (ARM, page