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

typedef long long ll;
typedef long double ld;
typedef complex<ld> cd;

typedef pair<int, int> pi;
typedef pair<ll,ll> pl;
typedef pair<ld,ld> pd;

typedef vector<int> vi;
typedef vector<ld> vld;
typedef vector<ll> vl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
typedef vector<cd> vcd;
typedef vector<bool> vb;
typedef tuple<int,int,int> ti;
typedef vector<string> vs;
typedef vector<double> vd;
typedef vector<vi> vii;
typedef vector<vii> viii;

template<class T> using PQ = priority_queue<T>;
template<class T> using PQG = priority_queue<T, vector<T>, greater<T>>;

#define rep(i, a, b) for (int i=a; i<(b); i++)
#define FOR(i, a) for (int i=0; i<(a); i++)
#define FORd(i,a,b) for (int i = (b)-1; i >= a; i--)
#define F0Rd(i,a) for (int i = (a)-1; i >= 0; i--)
#define trav(x,A) for (auto& x : A)

#define sz(x) (int)(x).size()
#define all(x) x.begin(), x.end()
#define mp make_pair
#define pb push_back
#define lb lower_bound
#define ub upper_bound
#define ins insert

const int MOD = 1000000007;
const char nl = '\n';

ll help(vl A, vl B) {
    int m = sz(A);

    int j = 0;
    ll mismatch = 0;
    ll match = 0;
    FORd(i, 0, m) {
        ll a = A[i];
        // I am 9, I want to match with 0
        while(j < m && i + j + 1 < m) j++;

        while(a && j < m) {
            ll b = B[j];
            ll cap = min(a, b);


            // cout << cap << " matches " << i << " " << j << nl;
            
            match += cap;
            a -= cap;
            B[j] -= cap;
            if (i + j >= m && cap > 0) mismatch++;

            if (B[j] == 0) j++;
        }
    }
    // cout << nl;

    if (match == 0) return 0;

    if (mismatch == 0) match--;
    return match;
}

int solve(int tt) {
    int m; cin >> m;

    vl A(m), B(m);
    trav(x, A) cin >> x;
    trav(x, B) cin >> x;

    ll x = accumulate(all(A), 0);
    ll y = accumulate(all(B), 0);

    int mx_a = 0;
    int mx_b = 0;

    rep(i, 0, m) {
        if (A[i]) mx_a = i;
        if (B[i]) mx_b = i;
    }

    if (mx_a + mx_b < m) {
        cout << 0 << nl;
        return 0;
    }

    if (x < y) {
        A[0] += y - x;
    } else {
        B[0] += x - y;
    }

    ll ans = max(help(A, B), help(B, A));
    cout << ans << nl;
    
    

    tt++;
    return 0;
}

int main() {
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);
    int T = 1;
    cin >> T;
    for (int i = 1; i <= T; i++) {
        if (solve(i)) break;
    }
    T++;
    return 0;
}