// #include <bits/stdc++.h>
#include <iostream>
#include <cmath>
#include <algorithm>
#include <map>
#include <vector>
#include <iomanip>
#include <string>
#include <queue>
#include <set>
#include <deque>
using namespace std;
#define int long long
const int N=3e5+5;
const int M=998244353;
const int LOG = 18;
int n , m , c , t=1 , q=1 , x , y;
vector<int>a(N),b(N),p(N);
void solve()
{
cin >> n;
for (int i=0;i<n;i++){
cin >> a[i];
}
int r=0;
for (int i=0;i<n;i++){
cin >> b[i];
r+=b[i];
}
int c=0;
for (int i=0;i<n;i++){
c+=a[i];
p[i]=c;
}
c=0;
int l=0;
int x=p[n-1];
int us=0;
int ri=r;
for (int i=n-1;i>0;i--){
x=min(x,p[i-1]);
int o=min(us,a[i]);
us-=o;
a[i]-=o;
if (x<ri-b[i]){
// cout << i << endl;
int u=min({ri-x,a[i],b[i]});
a[i]-=u;
b[i]-=u;
r-=u;
ri-=u;
}
int u=min(x,b[i]);
x-=u;
ri-=u;
b[i]-=u;
l+=u;
us+=u;
u=min(b[i],a[i]);
r-=u;
ri-=u;
}
int i=0;
x=0;
int o=min(us,a[i]);
us-=o;
a[i]-=o;
int u=min(x,b[i]);
x-=u;
b[i]-=u;
l+=u;
us+=u;
u=min(b[i],a[i]);
r-=u;
// cout << r << endl;
cout << 2*l-r << endl;
}
signed main()
{
ios::sync_with_stdio(0);//DO NOT USE IN INTERACTIVE
cin.tie(0), cout.tie(0);//DO NOT USE IN INTERACTIVE
cout << fixed<<setprecision(9);
// int t=1;
// cin >> t;
for (int _=1;_<=t;_++){
solve();
q++;
}
}
