#include<bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef pair<int,int> P;

#define p_ary(ary,a,b) do { cout << "["; for (int count = (a);count < (b);++count) cout << ary[count] << ((b)-1 == count ? "" : ", "); cout << "]\n"; } while(0)
#define p_map(map,it) do {cout << "{";for (auto (it) = map.begin();;++(it)) {if ((it) == map.end()) {cout << "}\n";break;}else cout << "" << (it)->first << "=>" << (it)->second << ", ";}}while(0)

template<typename T1,typename T2>ostream& operator<<(ostream& os,const pair<T1,T2>& a) {os << "(" << a.first << ", " << a.second << ")";return os;}

const char newl = '\n';

int main() {
    int n;
    cin >> n;
    vector<int> a(n),b(n);
    for (int i = 0;i < n;++i) cin >> a[i];
    for (int i = 0;i < n;++i) cin >> b[i];
    ll suma = 0,sumb = 0;
    for (int i = 0;i < n;++i) suma += a[i];
    for (int i = 0;i < n;++i) sumb += b[i];
    bool ok = true;
    ll ans = (suma-sumb)/(n-2);
    if (ans*(n-2) != suma-sumb) ok = false;
    int cnt = 0;
    for (int i = 0;i < n;++i) {
        if (a[i]-ans < b[i]) {
            if ((b[i]-a[i]+ans)%2 == 0) cnt += (b[i]-a[i]+ans)/2;
            else ok = false;
        } else if (b[i] < a[i]-ans) ok = false;
    }
    cout << (ok ? ans : -1) << endl;
}