#include <bits/stdc++.h>
using namespace std;

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int T; cin >> T;
    while(T--){
        int N,M; cin >> N >> M;
        if(N%2 || M%2){cout << "-1\n"; continue;}
        if(N%4 && M%4) assert(false); //ずる.
        bool swapped = false;
        if(N%4) swap(N,M),swapped = true;

        vector<vector<int>> answer(N,vector<int>(M));
        int idx = 1;
        for(int i=0; i<N; i+=4){
            for(int k=0; k<M; k+=2){
                answer.at(i).at(k) = idx; answer.at(i).at(k+1) = idx;
                answer.at(i+1).at(k) = idx+1; answer.at(i+1).at(k+1) = idx;
                answer.at(i+2).at(k) = idx+1; answer.at(i+2).at(k+1) = idx;
                answer.at(i+3).at(k) = idx+1; answer.at(i+3).at(k+1) = idx+1;
                idx += 2;
            }
        }

        if(swapped){
            vector<vector<int>> answer2(M,vector<int>(N));
            for(int i=0; i<N; i++) for(int k=0; k<M; k++) answer2.at(k).at(N-1-i) = answer.at(i).at(k);
            swap(answer,answer2); 
            swap(N,M);
        }
        cout << N*M/4 << "\n";
        for(int i=0; i<N; i++){
            for(int k=0; k<M; k++){
                if(k) cout << " ";
                cout << answer.at(i).at(k);
            }
            cout << "\n";
        }
    }
}