#include <iostream>
#include <algorithm>
#include <set>
#include <vector>
using namespace std;
const int N=2e5+10;
int a[N],gap[N];
bool dp[N][200];
pair<int,int> bt[N][200];
set<int> cur[N];
void solve()
{
int n,k;
cin>>n>>k;
for(int i=0;i<=n+1;i++)cur[i].clear();
a[0]=0;
for(int i=1;i<=k+1;i++)
{
if(i<=k)
cin>>a[i];
else{
a[i]=n+1;
}
gap[i]=a[i]-a[i-1]-1;
for(int x=a[i-1]+1;x<a[i];x++)cur[i].insert(x);
// cout<<"At "<<i<<' '<<cur[i].size()<<endl;
}
// gap[i]<=2
for(int i=0;i<=k+1;i++)for(int j=0;j<=n+1;j++)dp[i][j]=0;
dp[1][gap[1]]=1;
bt[1][gap[1]]={-1,-1};
for(int i=1;i<=k+1;i++)
{
for(int j=n+1;j>=3;j--)
{
if(!dp[i][j])continue;
dp[i][j-2]|=dp[i][j];
bt[i][j-2]={i,j};
}
for(int j=0;j<=n+1;j++)
{
if(!dp[i][j])continue;
if(j<=gap[i+1])
{
dp[i+1][gap[i+1]-j]|=dp[i][j];
bt[i+1][gap[i+1]-j]={i,j};
}
for(int k1=gap[i+1]-2;j<=k1 and gap[i+1]>2;)
{
dp[i+1][k1-j]|=dp[i][j];
bt[i+1][k1-j]={i+1,k1};
if(k1>2)k1-=2;
else break;
}
}
}
if(!dp[k+1][0])
{
cout<<-1<<endl;
return;
}
int i=k+1,j=0;
vector<int> ans;
while(i!=1 or j!=gap[1])
{
int ni=bt[i][j].first,nj=bt[i][j].second;
// cout<<"From "<<i<<' '<<j<<' '<<ni<<' '<<nj<<endl;
if(ni==i)
{
// cout<<cur[i].size()<<endl;
cur[i].erase(begin(cur[i]));
int x=*begin(cur[i]);
cur[i].erase(begin(cur[i]));
cur[i].erase(begin(cur[i]));
ans.push_back(x);
cur[i].insert(x);
}
else{
for(int p=0;p<nj;p++)
{
ans.push_back(a[ni]);
}
}
i=ni,j=nj;
}
cout<<ans.size()<<endl;
for(auto x:ans)cout<<x<<' ';
cout<<endl;
}
int main()
{
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t;
cin>>t;
while(t--)
{
solve();
}
}
