#include <string>
#include <vector>
#include <list>
#include <algorithm>
#include <map>
#include <set>
#include <iostream>
#include <cstdio>
#include <cstdlib>
using namespace std;

class BuyingFlowers {
  public:
    int buy(vector <int> roses, vector <int> lilies);
};

int is_valid(int r, int c, int tr, int tl)
{
  if (c%2 == 0 || r%2 == 0) return (tr == tl);
  return (tl == tr+1 || tr == tl+1);
}
  
int BuyingFlowers::buy(vector <int> roses, vector <int> lilies)
{
  int i, e, tr, tl, r, c;
  int min;

  min = 1000000;

  for (e = 1; e < (1 << roses.size()); e++) {
    tr = 0;
    tl = 0;
    for (i = 0; i < roses.size(); i++) {
      if (e & (1 << i)) {
        tr += roses[i];
        tl += lilies[i];
      }
    }
    for (r = 1; r*r <= (tr+tl); r++) {
      if ((tr+tl)%r == 0) {
        c = (tr+tl)/r;
        if (is_valid(r, c, tr, tl)) if (c-r < min) min = c-r;
      }
    }
  }
  if (min == 1000000) min = -1;
  return min;
}