#include <bits/stdc++.h>

void slv() {
  int m;
  std::cin >> m;
  std::vector<int> a(m);
  for (int i = 0; i < m; ++i) {
    std::cin >> a[i];
  }
  std::vector<int> b(m);
  for (int i = 0; i < m; ++i) {
    std::cin >> b[i];
  }
  a[0] = b[0] = std::numeric_limits<int>::max();

  bool flg = false, flg1 = false;
  for (int i = 1; i < m; ++i) {
    flg |= b[m - i] > 0;
    flg1 |= a[i] > 0 && flg;
  }
  int c = 0;
  bool flg2 = false;
  for (int i = 0, j = m - 1; i < m; ++i) {
    bool flg3 = c > 0;
    while (i + j >= m - 1) {
      int v = std::min(a[i], b[j]);
      a[i] -= v;
      b[j] -= v;
      c += v;
      flg2 |= i + j >= m && v > 0;
      if (a[i] == 0) {
        break;
      } else {
        --j;
      }
    }
    if (a[i] > 0) {
      flg2 |= flg3;
    }
  }

  if (flg2) {
    std::cout << c << "\n";
  } else if (flg1) {
    std::cout << c - 1 << "\n";
  } else {
    std::cout << 0 << "\n";
  }
}

int main() {
  std::cin.tie(nullptr)->sync_with_stdio(false);

  int t;
  std::cin >> t;
  for (int i = 0; i < t; ++i) {
    slv();
  }
  return 0;
}