#include <bits/stdc++.h>

// https://codeforces.com/blog/entry/96344

#pragma GCC optimize("O2,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")

using namespace std;

template <typename... Args>
void dbg(std::string const &str, Args &&...args) {
  std::cout << std::vformat(str, std::make_format_args(args...));
}

template <typename T>
void dbg(T const &t) {
  std::cout << t;
}

template <std::ranges::range T>
void dbgln(T const &t) {
  if constexpr (std::is_convertible_v<T, char const *>) {
    std::cout << t << '\n';
  } else {
    for (auto const &e : t) {
      std::cout << e << ' ';
    }
    std::cout << '\n';
  }
}

void dbgln() {
  std::cout << '\n';
}

template <typename... Args>
void dbgln(std::string const &str, Args &&...args) {
  dbg(str, std::forward<Args>(args)...);
  cout << '\n';
}

template <typename T>
void dbgln(T const &t) {
  dbg(t);
  cout << '\n';
}

template <typename T>
constexpr T MIN = std::numeric_limits<T>::min();

template <typename T>
constexpr T MAX = std::numeric_limits<T>::max();

template <typename T>
static T sc(auto &&x) {
  return static_cast<T>(x);
}

#define ff first
#define ss second
#define eb emplace_back
#define ll long long
#define ld long double
#define vec vector
#define endl '\n'

#define all(x) (x).begin(), (x).end()
#define rall(x) (r).rbegin(), (x).rend()
#define sz(x) static_cast<int>((x).size())
#define FOR(a, b, c) for (int(a) = (b); (a) < (c); ++(a))
#define ROF(a, b, c) for (int(a) = (b); (a) > (c); --(a))

void solve() {
  ll h, n;
  cin >> h >> n;

  vec<pair<ll, ll>> a(n);

  ll agg = 0;
  ll maxcooldown = MIN<ll>;

  FOR(i, 0, n) {
    cin >> a[i].ss;
  }
  FOR(i, 0, n) {
    cin >> a[i].ff;
    agg += a[i].ss;
    maxcooldown = max(maxcooldown, a[i].ff);
  }

  ll l = 0, r = maxcooldown * (ld)h / agg;

  while (l <= r) {
    ll t = l + (r - l) / 2;
    ll total = 0;
    for (auto [C, A] : a) {
      total += A * (1 + t / C);
    }
    if (total >= h) {
      r = t - 1;
    } else {
      l = t + 1;
    }
  }

  dbgln(l + 1);
}

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

  int t = 1;
  cin >> t;

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

  return 0;
}