#include <iostream>
#include <vector>
using namespace std;
int mp[1010][1010];
int main(){
    int t; cin >> t;
    while(t){
        t--;
        int i,j,n,m; cin >> n >> m;
        if(n&1 || m&1){
            cout << -1 << endl;
            return 0;
        }else{
            vector<pair<int,int>> v;
            for(j=0;j<m;j+=2){
               if((j/2)&1){
                   v.push_back({n - 2,j});
                   v.push_back({n - 1,j + 1});
                   v.push_back({n - 1,j});
                   v.push_back({n - 2,j + 1});
                   for(i=n - 3;i>0;i-=2){
                       v.push_back({i,j + 1});
                       v.push_back({i - 1,j});
                       v.push_back({i,j});
                       v.push_back({i - 1,j + 1});
                   }
               }else{
                   for(i=0;i<n - 2;i+=2){
                       v.push_back({i,j});
                       v.push_back({i + 1,j + 1});
                       v.push_back({i,j + 1});
                       v.push_back({i + 1,j});
                   }
                   v.push_back({n - 2,j});
                   v.push_back({n - 1,j + 1});
                   v.push_back({n - 1,j});
                   v.push_back({n - 2,j + 1});
               }
            }
            cout << v.size() << endl;
            for(i=0;i<v.size();i++){
                cout << v[i].first + 1 << " " << v[i].second + 1 << endl;
            }
            /*for(i=0;i<v.size();i++){
                mp[v[i].first][v[i].second] = i + 1;
            }
            for(i=0;i<n;i++){
                for(j=0;j<m;j++){
                    cout << mp[i][j] << " ";
                }
                cout << endl;
            }*/
        }
    }
}