#include <cassert>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <functional>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

using Int = long long;

template <class T1, class T2> ostream &operator<<(ostream &os, const pair<T1, T2> &a) { return os << "(" << a.first << ", " << a.second << ")"; };
template <class T> ostream &operator<<(ostream &os, const vector<T> &as) { const int sz = as.size(); os << "["; for (int i = 0; i < sz; ++i) { if (i >= 256) { os << ", ..."; break; } if (i > 0) { os << ", "; } os << as[i]; } return os << "]"; }
template <class T> void pv(T a, T b) { for (T i = a; i != b; ++i) cerr << *i << " "; cerr << endl; }
template <class T> bool chmin(T &t, const T &f) { if (t > f) { t = f; return true; } return false; }
template <class T> bool chmax(T &t, const T &f) { if (t < f) { t = f; return true; } return false; }


int N;
Int M;
vector<Int> A;

bool check(Int tar) {
  vector<Int> bs(N + 2, 0);
  for (int i = 1; i <= N; ++i) {
    bs[i] = (tar + A[i] - 1) / A[i];
  }
  vector<Int> cs(N + 2, 0), ds(N + 2, 0);
  vector<Int> fs(N + 2, 0), gs(N + 2, 0);
  for (int i = 1; i <= N; ++i) {
    fs[i] = fs[i - 1] + cs[i - 1];
    cs[i] = max((bs[i] - 1) - cs[i - 1], 0LL);
  }
  for (int i = N; i >= 1; --i) {
    gs[i] = gs[i + 1] + ds[i + 1];
    ds[i] = max((bs[i] - ((i == N) ? 1 : 2)) - ds[i + 1], 0LL);
  }
// cerr<<"tar = "<<tar<<", bs = "<<bs<<endl;
// cerr<<"  cs = "<<cs<<", fs = "<<fs<<endl;
// cerr<<"  ds = "<<cs<<", gs = "<<fs<<endl;
  for (int i = 1; i <= N; ++i) {
    // 0 -> N -> i
    Int cost = 0;
    cost += N;
    cost += (N - i);
    cost += 2 * fs[i - 1];
    cost += 2 * gs[i];
    cost += 2 * max(cs[i - 1], ds[i]);
    if (cost <= M) {
// cerr<<"  i = "<<i<<", cost = "<<cost<<endl;
      return true;
    }
  }
  return false;
}

int main() {
  for (int numCases; ~scanf("%d", &numCases); ) { for (int caseId = 1; caseId <= numCases; ++caseId) {
    scanf("%d%lld", &N, &M);
    A.resize(N + 1);
    for (int i = 1; i <= N; ++i) {
      scanf("%lld", &A[i]);
    }
    
    Int lo = 0;
    Int hi = M * *max_element(A.begin(), A.end()) / N + 1;
    for (; lo + 1 < hi; ) {
      const Int mid = (lo + hi) / 2;
      (check(mid) ? lo : hi) = mid;
    }
    printf("%lld\n", lo);
  }
#ifndef LOCAL
  break;
#endif
  }
  return 0;
}