Tidying Arrays

There are two arrays A[1..N] and B[1..N], each consisting of natural numbers from 1 to N. For an index i, one Swap(i) operation exchanges the values of A[i] and B[i].

The goal is to tidy the arrays so that no number appears more than once in A, and no number appears more than once in B.

Find the minimum possible number of Swap operations needed to achieve this. If it is impossible to make both arrays contain no duplicates, print -1.

The first line contains a natural number N (1 <= N <= 100000).

The second line contains A[1], A[2], ..., A[N], separated by spaces.

The third line contains B[1], B[2], ..., B[N], separated by spaces.

Every array element is a natural number between 1 and N, inclusive.

Print the minimum number of required Swap operations on the first line. If it is impossible, print -1.