#include<bits/stdc++.h>
#define int long long
using namespace std ;
const int maxn = 5e5+10 ;
int a[maxn],b[maxn] ;
int m ;
void solve(){
    cin >> m ;
    for(int i = 0 ; i < m ; i++)
        cin >> a[i] ;
    for(int i = 0 ; i < m ; i++)
        cin >> b[i] ;
    int suma = accumulate(a, a + m, 0ll);
    int sumb = accumulate(b, b + m, 0ll);
    int ans = 0 ;

    set<int> s;

    int mn = numeric_limits<int>::max(), ida = -1, idb = -1;

    for (int i = 0; i < m; i++) {
        if (a[i]) s.insert(i);
    }
    for (int i = 0; i < m; i++) {
        if (b[i]) {
            auto it = s.lower_bound(m - i);
            if (it != s.end()) {
                if (mn > *it + i) {
                    mn = *it + i;
                    ida = *it, idb = i;
                }
            }
        }
    }
    if (mn == numeric_limits<int>::max()) {
        cout << "0\n";
        return;
    }
    a[ida]-- ; b[idb]-- ;
    ans++ ;
    for(int i = 0 ; i < m ; i++)
    {
        int j = m-i-1 ;
        if(a[i]>=b[j]){
            a[i]-=b[j] ;
            ans+=b[j] ;
            b[j] = 0 ;
        }
        else{
            ans+=a[i] ;
            b[j]-=a[i] ;
            a[i] = 0 ;
        }
    }
    // cout<<"???"<<ans<<"\n" ;
    int mx = max(suma, sumb);
    if (suma < mx) {
        a[0] += mx - suma;
    } if (sumb < mx) {
        b[0] += mx - sumb;
    }
    for (int i = 0, j = m - 1; j >= 0; ) {
        while (i < m && a[i] == 0) i++;
        while (j >= 0 && b[j] == 0) j--;
        while (i < m && i + j < m - 1) i++;
        if (i == m || j == -1) break;
        int tmp = min(a[i], b[j]);
        a[i] -= tmp, b[j] -= tmp;
        ans += tmp;
    }

    cout << ans << "\n";
}
signed main(){
    ios::sync_with_stdio(false) ;
    cin.tie(0) ; cout.tie(0) ;
    int t ; cin >> t ; 
    while(t--)solve() ;
    return 0; 
}