#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;
constexpr int MOD=998244353;
#define rep(i,n) for(int i=0;i<(int)(n);i++)
void solve();
int main(){
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int test_case;
  cin>>test_case;
  while (test_case--){
    solve();
  }
}
void solve(){
  ll N,X;
  cin>>N>>X;
  vector C(N,0);
  for(int &i:C)cin>>i;
  reverse(C.begin(),C.end());
  ll ans=0;
  for(int i:C){
    if((X>>i&1)==0){
      if((1ll<<(i+1))<=X){
        ll t=X%(1ll<<(i+1));
        ans=min(t+1,(1ll<<i)-(X%(1ll<<i)))*2;
      }else{
        ans=((1ll<<i)-(X%(1ll<<i)))*2;
      }
      break;
    }
  }
  cout<<ans<<'\n';
}