# include <stdio.h>
# include <string.h>
# include <algorithm>
using namespace std;
int n,m,next[10010],a[1000010],b[10010];
void Getnext()
{
    int i=0,j=-1;
    next[0]=-1;
    while(i<m)
    {
        if(j==-1||b[i]==b[j])
            i++,j++,next[i]=j;
        else
            j=next[j];
    }
}
int KMP()
{
    int i=0,j=0;
    while(i<n&&j<m)
    {
        if(j==-1||a[i]==b[j])
            i++,j++;
        else
            j=next[j];
    }
    if(j==m)
        return i-j+1;
    return 0;
}
int  main()
{
    int t,i;
    while(~scanf("%d",&t))
    {
        while(t--)
        {
            scanf("%d%d",&n,&m);
            for(i=0;i<n;i++)
                scanf("%d",&a[i]);
            for(i=0;i<m;i++)
                scanf("%d",&b[i]);
            Getnext();
            int ans=KMP();
            if(ans)
                printf("%d\n",ans);
            else
                printf("-1\n");
        }
    }
    return 0;
}