#include <bits/stdc++.h>
using namespace std;
#define rep(i, a, b) for(int i = a; i < (b); i++)
#define all(x) begin(x),end(x)
#define sz(x) (int)(x).size()
typedef long long ll;
#define int ll
typedef pair<int, int> pii;
typedef vector<int> vi;

#define trav(a, x) for (auto& a: x)
#define f first
#define s second
#define pb push_back
const char nl = '\n';

#ifdef DBG
void dbg_out() { cerr << nl; }
template <typename Head, typename... Tail>
void dbg_out(Head H, Tail... T) {
    cerr << ' ' << H;
    dbg_out(T...);
}
#define dbg(...) dbg_out(__VA_ARGS__)
#else
#define dbg(...)
#endif

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());

signed main() {
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);
    int t; cin >> t;
    while (t--) {
        int m; cin >> m;
        int a[m], b[m];
        rep(i, 0, m) cin >> a[i];
        rep(i, 0, m) cin >> b[i];
        a[0] = b[0] = 1e15;
        // try all m options for which one adds to 10+
        // with 2 ptr
        // now we want the k-1 sums to >= m-1
        int leftover = 0;
        int ans = 0;
        bool ok = 0;
        vector<int> remA(m);
        vector<int> remB(m);
        for(int i = 0; i<m; i++){
            remA[i] = a[i];
            remB[i] = b[i];
        }
        rep(i, 0, m) {
            int cur = min(a[i], leftover+b[m-1-i]);
            // take from leftover first
            if (leftover > 0 && a[i] > 0) {
                ok = 1;
            }
            ans += cur;
            remA[i] -= cur;
            remB[m-1-i] -= cur;
            leftover = leftover+b[m-1-i]-cur;
        }
        int bigA = 0;
        int bigB = 0;
        for(int i = 0; i<m; i++){
            if(a[i]>0){
                bigA = i;
            }
            if(b[i]>0){
                bigB = i;
            }
        }
        for(int i = 0; i<m; i++){
            if(remA[i]>0 && i+bigB>=m){
                ok = 1;
            }
            if(remB[i]>0 && i+bigA>=m){
                ok = 1;
            }
        }
        if(!ok){
            ans--;
        }
        cout << ans << endl;
    }
}