#include <cstring>
#include <algorithm>
#include <cstdio>
#include <cstdlib>
#include <cmath>
using namespace std;
const int N=1000005,M=10005;
bool isd(char ch){
	return ‘0‘<=ch&&ch<=‘9‘;
}
void read(int &x){
	int f=1;
	x=0;
	char ch=getchar();
	while (!isd(ch)&&ch!=‘-‘)
		ch=getchar();
	if (ch==‘-‘)
		f=-1,ch=getchar();
	while (isd(ch))
		x=x*10+ch-48,ch=getchar();
	x*=f;
}
int T,n,m,a[N],b[M],Next[M];
int main(){
	read(T);
	while (T--){
		read(n),read(m);
		for (int i=0;i<n;i++)
			read(a[i]);
		for (int i=0;i<m;i++)
			read(b[i]);
		memset(Next,0,sizeof Next);
		int k=0;
		for (int i=1;i<m;i++){
			while (k&&b[k]!=b[i])
				k=Next[k-1];
			if (b[k]==b[i])
				k++;
			Next[i]=k;
		}
		int ans=-1;
		k=0;
		for (int i=0;i<n;i++){
			while (k&&b[k]!=a[i])
				k=Next[k-1];
			if (b[k]==a[i])
				k++;
			if (k==m){
				ans=i-m+2;
				break;
			}
		}
		printf("%d\n",ans);
	}
	return 0;
}