#include<iostream>

 #include<cstring>

 using namespace std;

 const int maxn = +;

 int n,m;

 int next[maxn];

 int a[maxn], b[maxn];

 void get_next()

 {

     int i = -, j = ;

     ::next[] = -;

     while (j < m)

     {

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

             ::next[++j] = ++i;

         else

             i = ::next[i];

     }

 }

 int kmp()

 {

     int i = , j = ;

     while (i < n)

     {

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

         {

             i++;

             j++;

         }

         else

             j = ::next[j];

         if (j == m)

             return i;

     }

     return -;

 }

 int main()

 {

     //freopen("D:\\txt.txt", "r", stdin);

     int t;

     cin >> t;

     while (t--)

     {

         cin >> n >> m;

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

             cin >> a[i];

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

             cin >> b[i];

         get_next();

         int k=kmp();

         if (k!=-)  cout << k-m+ << endl;

         else cout << "-1" << endl;

     }

     return ;

 }