#include <iostream>
#include <vector>
#include <cassert>
using namespace std;
using ll = long long int;

int main(){
    int t;
    cin >> t;
    assert(1 <= t <= 5);
    while(t--){
        int n, m;
        cin >> n >> m;
        assert(1 <= n <= 5000);
        assert(1 <= m <= 5000);
        vector<int> a(n), b(m);
        for(auto &p: a){
            cin >> p;
            assert(1 <= p <= 10000);
        }
        for(auto &p: b){
            cin >> p;
            assert(1 <= p <= 10000);
        }
        int ans = -1;
        for(int i = 0; i < n*m+10; i++){
            if(a[i%n] == b[i%m]){
                ans = i+1;
                break;
            }
        }
        cout << ans << endl;
    }
    return 0;
}