#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll=long long;
vector<vector<vector<int>>> v={{{0,0},{1,0},{2,0},{2,1}},{{0,1},{1,1},{0,2},{0,3}},{{2,2},{1,2},{1,3},{1,4}},{{2,3},{2,4},{2,5},{1,5}},{{0,4},{0,5},{0,6},{1,6}},{{0,7},{1,7},{2,7},{2,6}}};

int main()
{
    int t;
    cin>>t;
    while(t--){
        int n,m;
        cin>>n>>m;
        if(n==1||m==1||(n*m)%8!=0){
            cout<<-1<<endl;
            continue;
        }
        cout<<(n*m)/4<<endl;
        int k=(n*m)/4;
        vector<vector<int>> ans(n,vector<int>(m));
        if(n%2!=0){
            int cnt=1;
            for(int i=0;i<m/8;i++){
                for(int j=0;j<6;j++){
                    for(int l=0;l<4;l++){
                        ans[v[j][l][0]][v[j][l][1]+i*8]=j+i*6+1;
                    }
                    cnt++;
                }
            }
            for(int i=3;i<n;i+=2){
                for(int j=0;j<m;j+=4){
                    ans[i][j]=cnt;
                    ans[i+1][j]=cnt;
                    ans[i][j+1]=cnt;
                    ans[i][j+2]=cnt;
                    ans[i+1][j+1]=cnt+1;
                    ans[i+1][j+2]=cnt+1;
                    ans[i+1][j+3]=cnt+1;
                    ans[i][j+3]=cnt+1;
                    cnt+=2;
                }
            }
        }else if(m%2!=0){
            int cnt=1;
            for(int i=0;i<n/8;i++){
                for(int j=0;j<6;j++){
                    for(int l=0;l<4;l++){
                        ans[v[j][l][1]+i*8][v[j][l][0]]=j+i*6+1;
                    }
                    cnt++;
                }
            }
            for(int i=3;i<m;i+=2){
                for(int j=0;j<n;j+=4){
                    ans[j][i]=cnt;
                    ans[j][i+1]=cnt;
                    ans[j+1][i]=cnt;
                    ans[j+2][i]=cnt;
                    ans[j+1][i+1]=cnt+1;
                    ans[j+2][i+1]=cnt+1;
                    ans[j+3][i+1]=cnt+1;
                    ans[j+3][i]=cnt+1;
                    cnt+=2;
                }
            }

        }else if(n%4!=0){
            int cnt=1;
            for(int i=0;i<n;i+=2){
                for(int j=0;j<m;j+=4){
                    ans[i][j]=cnt;
                    ans[i+1][j]=cnt;
                    ans[i][j+1]=cnt;
                    ans[i][j+2]=cnt;
                    ans[i+1][j+1]=cnt+1;
                    ans[i+1][j+2]=cnt+1;
                    ans[i+1][j+3]=cnt+1;
                    ans[i][j+3]=cnt+1;
                    cnt+=2;
                }
            }

        }else{
            int cnt=1;
            for(int i=0;i<m;i+=2){
                for(int j=0;j<n;j+=4){
                    ans[j][i]=cnt;
                    ans[j][i+1]=cnt;
                    ans[j+1][i]=cnt;
                    ans[j+2][i]=cnt;
                    ans[j+1][i+1]=cnt+1;
                    ans[j+2][i+1]=cnt+1;
                    ans[j+3][i+1]=cnt+1;
                    ans[j+3][i]=cnt+1;
                    cnt+=2;
                }
            }
        }

        for(int i=0;i<n;i++){
            for(int j=0;j<m;j++){
                cout<<ans[i][j];
                if(j<m-1)cout<<" ";
            }
            cout<<endl;
        }
    }
    return 0;
}