#include <bits/stdc++.h>
#define int long long
using namespace std;
const int maxn = 2e6 + 5;
const int inf = 2e6;
int n,m;
int a[maxn],b[maxn];
void solve(){
	
	 cin >> n >> m;
	 int ans = 0;
	 for(int i = 1 ;i <= n ;i ++)
	 	   cin >> a[i];
	 for(int i = 1 ;i <= m ;i ++)
	       cin >> b[i];
	 priority_queue<int,vector<int>,greater<int> > q,h;
	 sort(a + 1, a + 1 + n);
	 sort(b + 1,b + 1 + m);
	 int t  = n - m;
	 for(int i = 1;i <= n ;i ++){
	 	if(i <= t) q.push(a[i]);
	    else{ 
	       if(a[i] > b[i - t]){
	       	  cout << -1 << endl;
	    	  return;
	        }
	     h.push(a[i]);ans += b[i - t] - a[i];
	    }
	 }
	 if(ans > t){
	 	   cout << -1 << endl;
	 	   return;
	 }
	 vector<int> nums;
	 int t1 = t - ans;
	 //cout << t1 << endl;
	 while(t1--){
	 	
	 	int k = q.top();
	 	q.pop();
	 	nums.push_back(k);
	 	if(k + 1 > h.top()){
	 	    int t = h.top();
	 	    h.pop();
	 	    h.push(k + 1);
	 	    q.push(t);
	 	    if(k + 1 <= b[1]) t1 ++;
	 	}
	 	else 
	 	  q.push(k + 1);
	 	q.pop();
	 	
	 }
	 for(int i = 1;i <= m ;i ++){
	     a[i] = h.top();
	     h.pop();
	     if(a[i] > b[i]){
	    	 cout << -1 << endl;
	    	 return;
	     }
	     while(b[i] > a[i]){
	     	   int k = q.top();
	     	   q.pop();
	     	   if(k + 1 > b[i]){
	     	   	     cout << - 1 << endl;
	     	   	     return;
	     	   }
	     	   q.push(k + 1);
	     	   q.pop();
	           nums.push_back(a[i]);
	           a[i] ++;
	     }
	 }
	 cout << nums.size() <<endl;
	 for(auto it : nums){
	 	  cout << it <<" ";
	 }
	 cout << endl;
	 
} 
signed main() {
    int t = 1;
     cin >> t;
    while (t--) {
       solve();
    }
    return 0;
}