#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int ct[2][6] = {0};
  for (int i = 0; i < n; i++) {
    int tmp;
    scanf("%d", &tmp);
    ct[0][tmp]++;
  }
  for (int i = 0; i < n; i++) {
    int tmp;
    scanf("%d", &tmp);
    ct[1][tmp]++;
  }
  int diff = 0;
  int flag = 0;
  for (int i = 1; i <= 5; i++) {
    if (ct[0][i] != ct[1][i]) {
      int tmp = abs(ct[0][i] - ct[1][i]);
      if (tmp % 2 != 0) flag = 1;
      diff += tmp / 2;
    }
  }
  if (flag == 0)
    cout << diff / 2;
  else
    cout << -1;
  return 0;
}
