#include<stdio.h>

#include<math.h>

#include<string.h>

#include<stdlib.h>

int a[], b[], next[];

int n, m;

void GetNext(int b[])//获得next数组

{

    int k = -, j = ;

    next[] = -;

    while(j < m)

    {

        if(k == - || b[j] == b[k])//b[k]表示前缀b[j]表示后缀

        {

            j++;

            k++;

            if(b[j] != b[k])

                next[j] = k;

            else

                next[j] = next[k];

        }

        else

            k = next[k];

    }

}

int KMP(int a[], int b[])

{

    int i = , j = ;

    while(i < n && j < m)

    {

        if(j == - || a[i] == b[j])//j == -1或当前字符匹配成功，则i++，j++

        {

            i++;

            j++;

        }

        else//j != -1 且当前字符匹配成功，b字符串向后移动j-next[j]位

            j = next[j];

    }

    if(j == m)

        return i - j + ;

    return -;

}

int main()

{

    int t, i;

    scanf("%d", &t);

    while(t--)

    {

        scanf("%d%d", &n, &m);

        for(i =  ; i < n ; i++)

            scanf("%d", &a[i]);

        for(i =  ; i < m ; i++)

            scanf("%d", &b[i]);

        GetNext(b);

        printf("%d\n", KMP(a, b));

    }

    return ;

}