#include<stdio.h>
#include<string.h>

const int MAXN = 1e6+7;

int mumStr[MAXN], sonStr[MAXN];
int Next[MAXN];

void GetNext(int s[], int N, int next[])
{
    int i=0, j=-1;
    next[0] = -1;

    while(i < N)
    {
        if(j==-1 || s[i]==s[j])
            next[++i] = ++j;
        else
            j = next[j];
    }
}
int KMP(int mumStr[], int sonStr[], int Mn, int Sn)
{
    int i=0, j=0;

    GetNext(sonStr, Sn, Next);

    while(i < Mn)
    {
        while(j==-1 || (mumStr[i]==sonStr[j]&&i<Mn&&j<Sn) )
            i++, j++;
        if(j == Sn)
            return i-Sn+1;
        j = Next[j];
    }

    return -1;
}

int main()
{
    int T;

    scanf("%d", &T);

    while(T--)
    {
        int i, Mn, Sn;

        scanf("%d%d", &Mn, &Sn);

        for(i=0; i<Mn; i++)
            scanf("%d", &mumStr[i]);
        for(i=0; i<Sn; i++)
            scanf("%d", &sonStr[i]);

        printf("%d\n", KMP(mumStr, sonStr, Mn, Sn));
    }

    return 0;
}