#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define rep(i, n) for(int i=0;i<(n);++i)
#define rep1(i, n) for(int i=1;i<=(n);i++)
#define ll long long
using mint = modint998244353;
using P = pair<ll,ll>;
using lb = long double;
using T = tuple<ll, ll, ll>;
#ifdef LOCAL
#  include <debug_print.hpp>
#  define dbg(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define dbg(...) (static_cast<void>(0))
#endif

int main()
{
    int t;
    cin >> t;
    while(t--) {
        ll n, x;
        cin >> n >> x;
        vector<int> c(n);
        rep(i,n) cin >> c[i];
        vector<ll> m(n), M(n);
        ll ans = 0;
        for(int i=n-1;i>=0;i--) {
            if(x>>c[i]&1) {
                m[i] = x;
                M[i] = x;
            }
            else{
                ll msk = 0;
                msk = (1<<c[i])-1;
                ll val = x&msk;
                m[i] = x-val-1;
                M[i] = x+(1<<c[i]) - val;
                if(m[i]>0) ans = min((M[i]-x)*2, (x-m[i])*2);
                else{
                    ans = (M[i]-x)*2;
                }
                break;
            }
        }    
        cout << ans << endl;
    }
    return 0;
}