#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 1000000000000000000LL

int main(){
	
	int _t;
	cin>>_t;
	rep(_,_t){
		int n,m;
		cin>>n>>m;
		if(n%2||m%2||(n%4&&m%4)){
			cout<<-1<<endl;
			continue;
		}
		cout<<(n*m)/4<<endl;
		vector<vector<int>> a(n,vector<int>(m));
		if(m%4==0){
			int cur = 1;
			for(int i=0;i<n;i+=2){
				for(int j=0;j<m;j+=4){
					a[i][j] = cur;
					a[i+1][j] = cur;
					a[i][j+1] = cur;
					a[i][j+2] = cur;
					cur++;
					a[i][j+3] = cur;
					a[i+1][j+1] = cur;
					a[i+1][j+2] = cur;
					a[i+1][j+3] = cur;
					cur++;
				}
			}
			
		}
		else{
			int cur = 1;
			for(int i=0;i<n;i+=4){
				for(int j=0;j<m;j+=2){
					a[i+1][j] = cur;
					a[i+2][j] = cur;
					a[i+3][j] = cur;
					a[i+3][j+1] = cur;
					cur++;
					a[i][j] = cur;
					a[i][j+1] = cur;
					a[i+1][j+1] = cur;
					a[i+2][j+1] = cur;
					cur++;
				}
			}
		}
		rep(i,n){
			rep(j,m){
				if(j!=0)cout<<' ';
				cout<<a[i][j];
			}
			cout<<endl;
		}
	}
	
	return 0;
}