#include <iostream>
#include <unordered_map>
#include <math.h>
using namespace std;

int main() {
    int numOfStudents, numOfStudents2;
    std::unordered_map<int,int> firstGroup;
    std::unordered_map<int,int> secondGroup;
    std::cin >> numOfStudents;
    numOfStudents2 = numOfStudents;
    while(numOfStudents--)
    {
        int a;
        std::cin >> a;
        ++firstGroup[a];
    }
    while(numOfStudents2--)
    {
        int a;
        std::cin >> a;
        ++secondGroup[a];
    }
    int diff = 0;
    for (int i = 1; i <= 5; ++i)
    {
        diff += std::abs(firstGroup[i] - secondGroup[i]);
    }
    if (diff % 4 != 0)
        std::cout << -1 << std::endl;
    else
        std::cout << diff / 4 << std::endl;
    return 0;
}