Hi, I'm writing my first program for my second year comsci class and I'm still learning java along the way. Anyways, the signature for one of my functions has to be:

"public static BigInteger fNumberRoutes( int n, int m )"

So I assume it's a function that returns a BigInteger.

Here's my code:

```
public static BigInteger fNumberRoutes( int n, int m ){
try{
if (n<0 || m<0)
{
throw new IllegalArgumentException("WTF?");
}
}
catch (IllegalArgumentException iAE){
System.out.println("Negative integer detected");
System.exit(1);
}
return 0;
}
}
```

Now, it doesn't really do anything yet, but this is my stub code. I get the following error message:

"CountRoutes2.java:29: cannot find symbol

symbol : class BigInteger

location: class CountRoutes2

public static BigInteger fNumberRoutes( int n, int m ){

^

1 error"

Not sure what I'm doing wrong. Maybe I don't completely understand what a BigInteger is, but I copied the assignment's signature exactly.

Thanks for the help.