I seem to be having trouble properly understanding the requirement of this question.

As per the following example, for `1`

in `num1`

, the next greater number in `num2`

is `3`

. Why is it not `2`

? Is it because `2`

already exists in `num1`

?

```
Input: nums1 = [4,1,2], nums2 = [1,3,4,2].
Output: [-1,3,-1]
Explanation:
For number 4 in the first array, you cannot find the next greater number for it in the second array, so output -1.
For number 1 in the first array, the next greater number for it in the second array is 3.
```

Thanks for any help.