#include <bits/stdc++.h>
using namespace std;
using int64 = long long;
int64 bit_count(int64 n) {
  int64 a{};
  while (n) {
    a += 1;
    n >>= 1;
  }
  return a;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int T;
  cin >> T;
  while (T--) {
    int64 n, m;
    cin >> n >> m;
    vector<int64> P(m);
    for (auto &p : P) cin >> p;
    auto s = accumulate(begin(P), end(P), 0ll);
    if (s < n) {
      cout << -1 << '\n';
      continue;
    }
    vector<int64> F(65);
    for (auto p : P) F[bit_count(p) - 1]++;
    int64 ans{};
    for (int i = 0, j = -1; i < 64; i++) {
      if (j >= 0 and F[i]) {
        ans += i - j;
        j = -1;
        F[i]--;
      }
      if (n & (1 << i)) {
        if (F[i]) {
          F[i]--;
        } else {
          if (j == -1) j = i;
        }
      }
      F[i + 1] += F[i] / 2;
    }
    cout << ans << '\n';
  }
}
