//ghost thread
#include<iostream>
#include<cstring>
#include<map>
#include<vector>
#include<queue>
#include<algorithm>
#include<set>
using namespace std;
#define int long long
int n,m;
int a[500000],b[500000];
priority_queue<int,vector<int>,greater<int>>qa,qb;
vector<int>res;
multiset<pair<int,int>>s;
int suma=0,sumb=0;
void add(int x){
    res.push_back(x);
    auto p=s.lower_bound(make_pair(x,n+1));
    p--;
    if((*p).second>=n-m+1) suma++;
    auto[val,id]=(*p);
    s.erase(p);s.insert(make_pair(val+1,id));
    s.erase(s.begin());
}
void solve(){
    cin>>n>>m;
    res.clear();s.clear();
    for(int i=1;i<=n;i++){
        cin>>a[i];
        s.insert(make_pair(a[i],i));
    }
    for(int i=1;i<=m;i++){
        cin>>b[i];
    }
    sort(a+1,a+1+n);
    sort(b+1,b+1+m);
    int cnt=0;
    suma=sumb=0;
    for(int j=1,i=n-m+1;j<=m&&i<=n;j++,i++){
        if(a[i]>b[j]){
            cout<<"-1\n";return ;
        }
        cnt+=b[j]-a[i];
        sumb+=b[j];suma+=a[i];
    }
    if(cnt>n-m){
        cout<<"-1\n";return ;
    }
    int tiks=0;
    while(sumb-suma<n-m-tiks&&s.size()>m){
        int w=(*s.begin()).first;
        add((*s.begin()).first);
        tiks++;
    }
    while(!qa.empty()) qa.pop();
    while(!qb.empty()) qb.pop();
    for(int i=1;i<=m;i++){
        int w=(*prev(s.end())).first;s.erase(prev(s.end()));
        a[i]=w;qa.push(a[i]);
        if(a[i]>b[m-i+1]){
            cout<<"-1\n";return ;
        }
    }
    for(int i=1;i<=m;i++) qb.push(b[i]);
    
    while(!qa.empty()){
        while(!qa.empty()&&qa.top()==qb.top()){
            qa.pop(),qb.pop();
        }
        if(qa.empty()) break;
        int w=qa.top();qa.pop();
        qa.push(w+1);res.push_back(w);
    }
    cout<<res.size()<<'\n';
    for(int x:res) cout<<x<<" ";cout<<'\n';
}

int32_t main(){
    ios::sync_with_stdio(false);cin.tie(0),cout.tie(0);
    int T;cin>>T;
    while(T--) solve();
}