#include<stdio.h>

#include<string.h>

const int MAXM = 1e4+;

const int MAXN = 1e6+;

int a[MAXN], b[MAXM], next_b[MAXM];

void GetNext(int b[], int next[], int M)

{

    int i=, j=-;

    next[] = -;

    while(i < M)

    {

        if(j==- || b[i]==b[j])

            next[++i] = ++j;

        else

            j = next[j];

    }

}

int KMP(int a[], int b[], int next[], int N, int M)

{

    int i = , j = ;

    while(i < N)

    {

        while(j==- || a[i] == b[j] && j<M)

            i++, j++;

        if(j == M)return i-M+;

        j = next[j];

    }

    return -;

}

int main()

{

    int T;

    scanf("%d", &T);

    while(T--)

    {

        int i, N, M;

        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, next_b, M);

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

    }

    return ;

}