I have the following issue: when trying to add to a sum of BigIntegers the outcome remains 0.

Here is the code:

```
public void NumberOfOutcomes(int x, int y){
BigInteger first = BigInteger.valueOf(0);
BigInteger second = BigInteger.valueOf(0);
for(int i = 0; i <= (x / 2); i++){
first.add( fac(x - i).divide((fac(x - 2*i).multiply(fac(i)))) );
System.out.println("First " + first.add( fac(x - i).divide((fac(x - 2*i).multiply(fac(i)))) ));
}
for(int i = 0; i <= (y / 2); i++){
second.add( fac(y - i).divide((fac(y - 2*i).multiply(fac(i)))) );
System.out.println("Second " + second.add( fac(y - i).divide((fac(y - 2*i).multiply(fac(i)))) ));
}
System.out.println("First " + first);
System.out.println("Second " + second);
System.out.println(first.multiply(second));
}
```

Here `fac`

is the factorial function.

Here is what come on the terminal:

points1.NumberOfOutcomes(2, 3)

First 1

First 1

Second 1

Second 2

First 0

Second 0

0