import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int t = sc.nextInt();
        for(int q = 0; q < t; q++){
          int n = sc.nextInt();
          int m = sc.nextInt();
          int[] a = new int[n];
          int[] b = new int[m];
          for(int i = 0; i < n; i++) a[i] = sc.nextInt();
          for(int i = 0; i < m; i++) b[i] = sc.nextInt();
          int ans = -1;
          for(int i = 0; i < n*m; i++){
            if(a[i%n] == b[i%m]){
              ans = i+1;
              break;
            }
          }
          System.out.println(ans);
        }
    }
}