#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
const int N=3*1e5+100;

int n,m,t,T,succ,a[N],b[N],c[N];
ll p,s;

priority_queue<int,vector<int>,greater<int> > q1,q2;

int main(){
	scanf("%d",&T);
	while (T--){
		scanf("%d%d",&n,&m);
		t=0;p=0;s=0;
		while (!q1.empty()) q1.pop();
		while (!q2.empty()) q2.pop();
		for (int i=1;i<=n;i++){
			scanf("%d",&a[i]);
			q1.push(a[i]);
			if (i>=n-m+1) q2.push(a[i]),s+=a[i];
		}
		for (int i=1;i<=m;i++){
			scanf("%d",&b[i]);
			p+=b[i];
		}
		while (q1.size()-m > p-s){
			c[++t]=q1.top();q1.pop();
			q1.push(c[t]+1);q1.pop();
			if (c[t]+1>q2.top()){
				s+=c[t]+1-q2.top();
				q2.pop();
				q2.push(c[t]+1);
			}
		}
		if (q1.size()-m == p-s){
			for (int i=1;i<=m;i++){
				a[i]=q2.top();
				q2.pop();
			}
			succ=1;
			for (int i=1;i<=m;i++){
				if (a[i]>b[i]) succ=0;
				while (a[i]<b[i]) c[++t]=a[i]++;
			}
			if (succ){
				printf("%d\n",n-m);
				for (int i=1;i<=t;i++) printf("%d ",c[i]);
				puts("");
			}else puts("-1");
		}else puts("-1");
	}
	return 0;
}