#include<bits/stdc++.h>
using i64 = long long;

int main(){
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr), std::cout.tie(nullptr);
    
    int t;
    std::cin >> t;
    while (t--) {
        int n; std::cin >> n;
        std::vector<i64> a(n), b(n);
        i64 sa = 0, sb = 0;
        int mxa = 0, mxb = 0;
        for (int i = 0; i < n; i++) std::cin >> a[i], sa += a[i];
        for (int i = 0; i < n; i++) std::cin >> b[i], sb += b[i];
        for (int i = 0; i < n; i++) {
            if (a[i]) mxa = i;
            if (b[i]) mxb = i;
        }
        if (mxa + mxb < n) {
            std::cout << 0 << "\n";
            continue;
        }

        if (sa < sb) a[0] += sb - sa;
        else b[0] += sa - sb;

        i64 ans = 0;
        bool ok = true;
        int l = 0, r = n - 1;

        while (l < n) {
            while (l < n && !a[l]) l++;
            while (r >= 0 && !b[r]) r--;
            if (l == n || r == -1) break;
            if (l + r + 1 < n) {
                l++;
                continue;
            } else if (l + r + 1 >= n) {
                int d = std::min(a[l], b[r]);
                a[l] -= d, b[r] -= d;
                ans += d;
                if (l + r + 1 > n) ok = false;
            }
        }

        for (int i = 1; i < n; i++) {
            if (a[i] && i <= mxa) ok = false;
            if (b[i] && i <= mxb) ok = false;
        }
        std::cout << ans - ok << "\n";
        
    }
    return 0;
}