#include<stdio.h>
#include<iostream>
#include<string.h>
#include<algorithm>
using namespace std;
int s[1000005],t[10005];
int Next[1000005];
int ans;
void getNext(int b){
   int i=0,j=-1;
   Next[0]=-1;
   while(i<b){
      if(j==-1||t[i]==t[j]){
        i++;
        j++;
        Next[i]=j;
      }
    else
        j=Next[j];
   }
}
int kmp(int a,int b){
    int i=0,j=0,sum=0;
    while(i<a){
        if(j==-1||s[i]==t[j]){
            i++;
            j++;
        }
        else
            j=Next[j];
        if(j==b){
            ans=i+1-b;///该步需要特别注意一下即可
            return ans;
        }
    }
    return -1;
}
int main(){
   int tt;
   scanf("%d",&tt);
   while(tt--){
      memset(s,0,sizeof(s));
      memset(t,0,sizeof(t));
      memset(Next,0,sizeof(Next));
      int t1,t2;
      scanf("%d%d",&t1,&t2);
     int temp;
      for(int i=0;i<t1;i++){
         scanf("%d",&s[i]);
      }
           for(int i=0;i<t2;i++){
           scanf("%d",&t[i]);
           }
      getNext(t2);
      int pd;
      pd=kmp(t1,t2);
      printf("%d\n",pd);

   }
   return 0;
}