#include <bits/stdc++.h>
using namespace std;
long long mod = 1000000007;
long long mod2 = 998244353;
long long mod3 = 1000003;
long long mod4 = 998244853;
long long inf = 1LL << 60;
long double pi = 3.14159265358979323846L;
double eps = 1e-12;
int dh[4] = {1, -1, 0, 0};
int dw[4] = {0, 0, 1, -1};
int ddh[8] = {-1, -1, -1, 0, 0, 1, 1, 1};
int ddw[8] = {-1, 0, 1, -1, 1, -1, 0, 1};
long long gcd(long long a, long long b) {
  if (a < b) swap(a, b);
  if (b == 0) return a;
  if (a % b == 0) return b;
  return gcd(b, a % b);
}
long long Pow(long long n, long long k) {
  long long ret = 1;
  long long now = n;
  while (k > 0) {
    if (k & 1) ret *= now;
    now *= now;
    k /= 2;
  }
  return ret;
}
long long beki(long long n, long long k, long long md) {
  long long ret = 1;
  long long now = n;
  while (k > 0) {
    if (k % 2 == 1) {
      ret *= now;
      ret %= md;
    }
    now *= now;
    now %= md;
    k /= 2;
  }
  return ret;
}
long long gyaku(long long n, long long md) { return beki(n, md - 2, md); }
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int t;
  cin >> t;
  for (long long i = 0; i < t; i++) {
    long long n, m;
    cin >> n >> m;
    long long a[m];
    long long sum = 0;
    unordered_map<long long, long long> mp;
    for (long long j = 0; j < m; j++) {
      cin >> a[j];
      sum += a[j];
      mp[a[j]]++;
    }
    if (sum < n) {
      cout << -1 << endl;
      continue;
    }
    unordered_map<long long, bool> ok;
    long long nn = n;
    for (long long j = 0; j < 60; j++) {
      long long now = 1LL << j;
      if (nn % 2) {
        ok[now] = false;
      } else
        ok[now] = true;
      nn /= 2;
    }
    long long now = 1;
    sum = 0;
    set<long long> st;
    long long ans = 0;
    for (;;) {
      sum += mp[now] * now;
      if (mp[now] > 0) {
        long long u = *st.begin();
        long long uu = now;
        while (uu > u) {
          ans++;
          uu /= 2;
        }
        for (auto itr = st.begin(); itr != st.end(); itr++) {
          sum -= *itr;
        }
        st.clear();
      }
      if (ok[now] == false) {
        if (sum >= now) {
          sum -= now;
          ok[now] = true;
        } else {
          st.insert(now);
        }
      }
      now *= 2;
      if (now > 1000000000000000000) break;
    }
    cout << ans << endl;
  }
}
