#ifdef NACHIA
#define _GLIBCXX_DEBUG
#else
#define NDEBUG
#endif
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
using i64 = long long;
using u64 = unsigned long long;
#define rep(i,n) for(int i=0; i<int(n); i++)
const i64 INF = 1001001001001001001;
template<typename A> void chmin(A& l, const A& r){ if(r < l) l = r; }
template<typename A> void chmax(A& l, const A& r){ if(l < r) l = r; }
#include <atcoder/modint>
using Modint = atcoder::static_modint<998244353>;
using namespace std;

void testcase(){
    int N, M; cin >> N >> M;
    if(N % 2 == 1 || M % 2 == 1){ cout << "-1\n"; return; }
    if(N % 4 == 2 && M % 4 == 2){ cout << "-1\n"; return; }
    bool f = M % 4 == 2;
    if(f) swap(N, M);
    vector<vector<int>> ans(N, vector<int>(M));
    rep(i,N/2) rep(j,M/4){
        int x = j * N + i * 2 + 1;
        ans[i*2+0][j*4+0] = x+0;
        ans[i*2+0][j*4+1] = x+0;
        ans[i*2+0][j*4+2] = x+0;
        ans[i*2+0][j*4+3] = x+1;
        ans[i*2+1][j*4+0] = x+0;
        ans[i*2+1][j*4+1] = x+1;
        ans[i*2+1][j*4+2] = x+1;
        ans[i*2+1][j*4+3] = x+1;
    }
    if(f) swap(N, M);
    cout << (N*M/4) << "\n";
    if(f){
        rep(i,N){
            rep(j,M){
                if(j) cout << " ";
                cout << ans[j][i];
            } cout << "\n";
        }
    } else {
        rep(i,N){
            rep(j,M){
                if(j) cout << " ";
                cout << ans[i][j];
            } cout << "\n";
        }
    }
}

int main(){
    ios::sync_with_stdio(false); cin.tie(nullptr);
    int T; cin >> T;
    rep(t,T) testcase();
    return 0;
}