#if __INCLUDE_LEVEL__ == 0

#include __BASE_FILE__

namespace {

void solve() {
  int m;
  scan(m);
  std::vector<i64> a(m);
  scan(a);
  std::vector<i64> b(m);
  scan(b);

  {
    const i64 sum_a = std::accumulate(a.begin(), a.end(), i64{0});
    const i64 sum_b = std::accumulate(b.begin(), b.end(), i64{0});
    if (sum_a < sum_b) {
      a[0] += sum_b - sum_a;
    } else if (sum_b < sum_a) {
      b[0] += sum_a - sum_b;
    }
  }

  i64 ans = 0;
  i64 cur = 0;
  bool ok = false;
  int count = 0;
  for (const int i : rep(m)) {
    const bool rest = 0 < cur;
    cur += b[m - i - 1];
    const i64 t = std::min(a[i], cur);
    if (0 < t) {
      if (rest) {
        ok = true;
      }
      ++count;
    }
    ans += t;
    cur -= t;
  }

  if (!ok) {
    if (count == 1) {
      ans = 0;
    } else {
      --ans;
    }
  }

  print(ans);
}

}  // namespace

int main() {
  std::ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  std::cout << std::setprecision(DBL_DECIMAL_DIG);

  int t;
  scan(t);
  while (t--) {
    solve();
  }
}

#else  // __INCLUDE_LEVEL__

#include <bits/stdc++.h>

template <class T, class U = T>
bool chmin(T& x, U&& y) {
  return y < x && (x = std::forward<U>(y), true);
}

template <class T, class U = T>
bool chmax(T& x, U&& y) {
  return x < y && (x = std::forward<U>(y), true);
}

template <std::signed_integral T = int>
T inf() {
  T ret;
  std::memset(&ret, 0x3f, sizeof(ret));
  return ret;
}

template <std::floating_point T>
T inf() {
  return std::numeric_limits<T>::infinity();
}

template <class T>
concept Range = std::ranges::range<T> && !std::convertible_to<T, std::string_view>;

template <class T>
concept Tuple = std::__is_tuple_like<T>::value && !Range<T>;

namespace std {

istream& operator>>(istream& is, Range auto&& r) {
  for (auto&& e : r) {
    is >> e;
  }
  return is;
}

istream& operator>>(istream& is, Tuple auto&& t) {
  return apply([&](auto&... xs) -> istream& { return (is >> ... >> xs); }, t);
}

ostream& operator<<(ostream& os, Range auto&& r) {
  for (string_view sep = ""; auto&& e : r) {
    os << exchange(sep, " ") << e;
  }
  return os;
}

ostream& operator<<(ostream& os, Tuple auto&& t) {
  const auto f = [&](auto&... xs) -> ostream& {
    [[maybe_unused]] string_view sep = "";
    ((os << exchange(sep, " ") << xs), ...);
    return os;
  };
  return apply(f, t);
}

}  // namespace std

void scan(auto&&... xs) { std::cin >> std::tie(xs...); }
void print(auto&&... xs) { std::cout << std::tie(xs...) << '\n'; }

template <class F>
class fix {
 public:
  explicit fix(F f) : f_(std::move(f)) {}

  decltype(auto) operator()(auto&&... xs) const {
    return f_(std::ref(*this), std::forward<decltype(xs)>(xs)...);
  }

 private:
  F f_;
};

inline auto rep(int l, int r) { return std::views::iota(std::min(l, r), r); }
inline auto rep(int n) { return rep(0, n); }
inline auto rep1(int l, int r) { return rep(l, r + 1); }
inline auto rep1(int n) { return rep(1, n + 1); }

namespace ranges = std::ranges;
namespace views = std::views;

using i64 = std::int64_t;

#endif  // __INCLUDE_LEVEL__