#include <bits/stdc++.h>
using namespace std;
#define int long long
typedef pair<int,int> P;
int INF = 1e9+7;
int mod = 1e9+7;
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};
signed main() {
    int N;
    cin >> N;
    vector<int>A(N);
    vector<int>B(N);
    int sum = 0;
    for(int i = 0; i < N; i++) {
        cin >> A[i];
        sum+=A[i];
    }
    int sum2 = 0;
    for(int i = 0; i < N; i++) {
        cin >> B[i];
        sum2+=B[i];
    }
    if(N == 2) {
        cout << abs(A[0]-B[0]) << endl;
        return 0;
    }
    // 190 185
    if(abs(sum-sum2)%(N-2) == 0 && sum >= sum2) {
        int MA = (sum-sum2)/(N-2);
        int cnt = MA;
        int ans = 0;
        for(int i = 0; i < N; i++) {
            if(A[i]-MA < B[i]) {
                if((B[i]-(A[i]-MA))/2 > cnt) {
                    cout << -1 << endl;
                    return 0;
                }
                ans+=(B[i]-(A[i]-MA))/2;
                cnt-=(B[i]-(A[i]-MA))/2;
            }
        }
        cout << ans << endl;
    }
    else {
        cout << -1 << endl;
    }
}