#include <bits/stdc++.h>
/*#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>*/
#define ll long long
#define ll1 long long
#define ull unsigned long long
#define dou long double
#define str string
#define vll vector<ll>
#define vi vector<int>
#define pll pair<ll, ll>
#define vpll vector<pll>
#define vbool vector<bool>
#define vstr vector<str>
#define vvll vector<vll>
#define pb push_back
#define pf push_front
#define endl "\n"
#define fr first
#define se second
// #define sortcmp(a) sort(a.begin(), a.end(), cmp)
#define sort(a) sort(a.begin(), a.end())
#define reverse(a) reverse(a.begin(), a.end())
#define speed ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define INF 5000000000000000000
#define ordered_set tree<ll, null_type, less_equal<ll>, rb_tree_tag, tree_order_statistics_node_update>
using namespace std;
//using namespace __gnu_pbds;
mt19937 rng(1488);
ll randll(ll l, ll r){
    return uniform_int_distribution<ll>(l, r)(rng);
}
int main() {
    speed;
    srand(time(0));
    ll t;
    cin >> t;
    while (t --) {
        ll n, k;
        cin >> n >> k;
        vll a;
        a.pb(0);
        for (int i = 0; i < k; i ++) {
            ll b;
            cin >> b;
            a.pb(b);
        }
        a.pb(n+1);
        vll b;
        for (int i = 1; i < a.size(); i ++) {
            b.pb(a[i]-a[i-1]-1);
            //cout << a[i]-a[i-1]-1 << ' ';
        }
        //cout << endl;
        vbool dp[2];
        dp[0].resize(n, 0);
        dp[1].resize(n, 0);
        dp[0][0] = 1;
        if (b[0] == 0) {
            dp[0][0] = 0;
            dp[1][0] = 1;
        }
        for (int i = 1; i < b.size(); i ++) {
            if (b[i] == 0) {
                if (dp[1][i-1]) dp[1][i] = 1;
                //cout << dp[0][i] << ' ' << dp[1][i] << endl;
                continue;
            }
            if (dp[0][i-1]) {
                if (b[i-1] % 2 == 1 && b[i] % 2 == 1) {
                    dp[1][i] = 1;
                }
                if (b[i-1] % 2 == 0) {
                    if (b[i] % 2 == 1 && b[i] > 1) dp[0][i] = 1;
                    if (b[i] % 2 == 0) dp[1][i] = 1;
                }
            }
            if (dp[1][i-1]){
                dp[0][i] = 1;
                if (b[i] % 2 == 0 && b[i-1] > 2) dp[1][i] = 1;
            }
            //cout << dp[0][i] << ' ' << dp[1][i] << endl;
        }
        if (!dp[1][b.size()-1]) {
            cout << -1 << endl;
            continue;
        }
        ll k1 = 1;
        vll res;
        vll c = b;
        for (int i = b.size()-1; i > 0; i --) {
            if (b[i] == 0) continue;
            if (dp[0][i-1]) {
                if (b[i-1] % 2 == 1 && b[i] % 2 == 1 && k1) {
                    c[i] --;
                    c[i-1] --;
                    res.pb(a[i]);
                    k1 = 0;
                    continue;
                }
                if (b[i-1] % 2 == 0) {
                    if (b[i] % 2 == 1 && b[i] > 1 && !k1) {
                        c[i] -= 2;
                        c[i-1] -= 2;
                        res.pb(a[i]);
                        res.pb(a[i]);
                        continue;
                    }
                    if (b[i] % 2 == 0 && k1) {
                        c[i] -= 2;
                        c[i-1] -= 2;
                        res.pb(a[i]);
                        res.pb(a[i]);
                        k1 = 0;
                        continue;
                    }
                }
            }
            if (dp[1][i-1]){
                if (!k1) {
                    k1 = 1;
                    continue;
                }
                if (b[i] % 2 == 0 && b[i-1] > 2 && k1) {
                    c[i] -= 2;
                    c[i-1] -= 2;
                    res.pb(a[i]);
                    res.pb(a[i]);
                    k1 = 0;
                }
            }
        }
        for (int i = 0; i < c.size(); i ++) {
            for (int j = 0; j < c[i]/2; j ++) {
                res.pb((a[i]+a[i+1])/2);
            }
        }
        reverse(res);
        cout << res.size() << endl;
        for (int i : res) {
            cout << i << ' ';
        }
        cout << endl;
    }
}
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