1 //2016.10.7
 2 #include <iostream>
 3 #include <cstdio>
 4 #include <cstring>
 5 
 6 using namespace std;
 7 
 8 const int inf = 0x3f3f3f3f;
 9 int a[1000005], b[10005], nex[10005];
10 
11 int kmp(int a[], int b[])
12 {
13     int ans = 0;
14     nex[0] = -1;
15     for(int i = 0, fail = -1; b[i] != inf;)//求nex数组， fail为失配指针
16     {
17         if(fail==-1 || b[i] == b[fail])
18         {
19             i++, fail++;
20             nex[i] = fail;
21         }else fail = nex[fail];
22     }
23     int i = 0, j = 0;
24     for(; a[i] != inf; i++, j++)
25     {
26         if(j != -1 && b[j] == inf)return i-j+1;
27         while(j != -1 && a[i] != b[j])j = nex[j];
28     }
29     if(b[j] == inf)return i-j+1;
30     return -1;
31 }
32 
33 int main()
34 {
35     int T, n, m;
36     scanf("%d", &T);
37     while(T--)
38     {
39         scanf("%d%d", &n, &m);
40         for(int i = 0; i < n; i++)scanf("%d", &a[i]);
41         for(int i = 0; i < m; i++)scanf("%d", &b[i]);
42         a[n] = b[m] = inf;//设置截止符号
43         printf("%d\n", kmp(a, b));
44     }
45 
46     return 0;
47 }