#include<iostream>
#include<vector>

using namespace std;

int solve(){
    int N,M;
    cin >> N >> M;
    vector<int> A(N),B(M);

    for (int i=0; i<N; i++) cin >> A[i];
    for (int j=0; j<M; j++) cin >> B[j];

    for (int k=0; k<N*M; k++) if (A[k%N]==B[k%M]) return k+1;
    return -1;
}

int main(){
    int T;
    cin >> T;

    while (T--){
        cout << solve() << endl;
    }
}