#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main(){
    int TT;
    cin>>TT;
    set<pair<int,int>> s;
    s.insert({0,0});
    s.insert({0,1});
    s.insert({0,2});
    s.insert({1,0});
    while(TT--){
    	int N,M;
    	cin>>N>>M;
    	if(N%4 == 0 && M%2 == 0){
    		cout<<N*M/4<<endl;
    		for(int i=0;i<N;i++){
    			for(int j=0;j<M;j++){
    				int t = (i/4)*(M/2)+j/2;
    				int x = j%2, y = i%4;
    				cout<<(s.count({x,y}) ? 2*t+1 : 2*t+2)<<' ';
    			}
    			cout<<endl;
    		}
    		continue;
    	}
    	else if(M%4 == 0 && N%2 == 0){
    		cout<<N*M/4<<endl;
    		for(int i=0;i<N;i++){
    			for(int j=0;j<M;j++){
    				int t = (i/2)*(M/4)+j/4;
    				int x = i%2, y = j%4;
    				cout<<(s.count({x,y}) ? 2*t+1 : 2*t+2)<<' ';
    			}
    			cout<<endl;
    		}
    		continue;
    	}
    	else{
    		cout<<-1<<endl;
    	}
    }
}