#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define eb emplace_back
//mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
#define mod 998244353
#define ll long long
#define inf 0x3f3f3f3f
#define INF 0x3f3f3f3f3f3f3f3f
inline int read()
{
	char ch=getchar(); int nega=1; while(!isdigit(ch)) {if(ch=='-') nega=-1; ch=getchar();}
	int ans=0; while(isdigit(ch)) {ans=ans*10+ch-48;ch=getchar();}
	if(nega==-1) return -ans;
	return ans;
}
void print(vector<int> x){for(int i=0;i<(int)x.size();i++) printf("%d%c",x[i]," \n"[i==(int)x.size()-1]);}
#define N 300005
int a[N],b[N],n,m;
struct Node
{
	int v,id;
	bool operator < (const Node &x) const
	{
		if(v!=x.v) return v>x.v;
		return id<x.id;
	}
};
int attempt()
{
	int w=0;
	sort(a+1,a+n+1,greater<int>());
	sort(b+1,b+m+1,greater<int>());
	for(int i=1;i<=m;i++)
	{
		if(a[i]>b[i]) return -1;
		w+=b[i]-a[i];
	}
	int go=n-m;
	int res=go-w;
	return res;
}
void work()
{
	n=read(),m=read();
	for(int i=1;i<=n;i++) a[i]=read();
	for(int i=1;i<=m;i++) b[i]=read();
	set<Node> s;
	for(int i=1;i<=n;i++) s.insert((Node){a[i],i});
	int pre=attempt();
	sort(b+1,b+m+1);
	// cout<<pre<<endl;
	vector<int> ans;
	for(int i=1;i<=pre;i++)
	{
		auto [w,id]=*s.rbegin();
		// printf("* %d %d\n",w,id);
		w++; ans.pb(w-1);
		s.erase(--s.end());
		s.insert((Node){w,id});
		s.erase(--s.end());
	}
	for(int i=m;i>=1;i--)
	{
		if(s.begin()->v>b[i])
		{
			cout<<"-1\n";
			return ;
		}
		while(s.begin()->v<b[i])
		{
			if(s.empty())
			{
				cout<<"-1\n";
				return ;
			}
			auto [w,id]=*s.begin();
			w++; ans.pb(w-1);
			s.erase(s.begin());
			s.insert((Node){w,id});
			s.erase(--s.end());
		}
		s.erase(s.begin());
	}
	while((int)ans.size()<n-m)
	{
		auto [w,id]=*s.rbegin();
		w++; ans.pb(w-1);
		if(w>b[m])
		{
			cout<<"-1\n";
			return ;
		}
		s.erase(--s.end());
		s.insert((Node){w,id});
		s.erase(--s.end());
	}
	cout<<ans.size()<<endl;
	print(ans);
}
signed main()
{
	int T=read(); while(T--) work();
	return 0;
}