Just add them all up, and subtract the total you would expect if only 1001 numbers were used from that.

Eg:

```
Input: 1,2,3,2,4 => 12
Expected: 1,2,3,4 => 10
Input - Expected => 2
```

Just add them all up, and subtract the total you would expect if only 1001 numbers were used from that.

Eg:

```
Input: 1,2,3,2,4 => 12
Expected: 1,2,3,4 => 10
Input - Expected => 2
```