#include <bits/stdc++.h>
#define NM 100002
using namespace std;
int t;
int n, q;
int p[NM];
int v[NM];
deque <int> op;
int dp[NM][3], dp1[NM][3];
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
cin >> t;
while(t--)
{
cin >> n >> q;
for(int i = 1; i <= q; i++)
cin >> p[i];
q++;
p[q] = n + 1;
int sum = 0;
for(int i = 1; i <= q; i++)
{
v[i] = p[i] - p[i - 1] - 1;
sum += v[i];
}
for(int i = 0; i < q; i++)
for(int j = 0; j <= 2; j++)
dp[i][j] = 0;
dp[0][0] = 1;
for(int i = 0; i < q - 1; i++)
for(int j = 0; j <= 2; j++)
{
if(dp[i][j] == 0)
continue;
if((j > 0 || v[i + 1] == 0) && (v[i + 1] - j) % 2 == 0 && v[i + 1] >= j)
{
dp[i + 1][0] = 1;
dp1[i + 1][0] = j;
}
if(v[i + 1] >= j + 1 && (v[i + 1] - (j + 1)) % 2 == 0 && v[i + 2] >= 1)
{
dp[i + 1][1] = 1;
dp1[i + 1][1] = j;
}
if(v[i + 1] >= j + 2 && (v[i + 1] - (j + 2)) % 2 == 0 && v[i + 2] >= 2)
{
dp[i + 1][2] = 1;
dp1[i + 1][2] = j;
}
}
if(!(dp[q - 1][1] || dp[q - 1][2] || dp[q - 1][0]))
{
cout << "-1\n";
continue;
}
int cnt;
if(dp[q - 1][0])
cnt = 0;
else if(dp[q - 1][1])
cnt = 1;
else
cnt = 2;
cout << sum / 2 << "\n";
for(int j = 1; j <= (v[q] - cnt) / 2; j++)
cout << p[q - 1] + (v[q] + 1) / 2 << " ";
for(int i = q - 1; i >= 1; i--)
{
int val = cnt + dp1[i][cnt];
for(int j = 1; j <= (v[i] - val) / 2; j++)
cout << p[i - 1] + (v[i] + 1) / 2 << " ";
for(int j = 1; j <= cnt; j++)
cout << p[i] << " ";
cnt = dp1[i][cnt];
}
cout << "\n";
}
return 0;
}
