#include "bits/stdc++.h" using namespace std; #define int long long #define rep(i,n) for(int i=0;i<n;i++) #define vi vector<int> #define all(a) a.begin(),a.end() typedef pair<int,int> P; constexpr long long mod=1000000007; constexpr long long inf=1ll<<61; int a[100006],b[100006]; signed main(){ int n;cin>>n; rep(i,n)cin>>a[i]; rep(i,n)cin>>b[i]; int s=0; rep(i,n)s+=a[i]; rep(i,n)s-=b[i]; if(n==2){ if(a[0]+a[1]==b[0]+b[1]){ cout<<abs(a[0]-b[0])<<endl; } else cout<<-1<<endl; return 0; } if(s<0||s%(n-2))cout<<-1<<endl; else{ int k=s/(n-2); rep(i,n)a[i]-=k; int cnt=0; rep(i,n){ if(a[i]>b[i]){ cout<<-1<<endl;return 0; } else if((b[i]-a[i])&1){ cout<<-1<<endl;return 0; } else{ cnt+=(b[i]-a[i])/2; } } if(k==cnt){ cout<<k<<endl; } else{ cout<<-1<<endl; } } }