#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <cmath>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <algorithm>
#include <complex>
#include <unordered_map>
#include <unordered_set>
#include <random>
#include <cassert>
#include <fstream>
#include <utility>
#include <functional>
#include <stack>
#define popcount __builtin_popcount
using namespace std;
typedef long long int ll;
typedef pair<int, int> P;

int main()
{
    int t; cin>>t;
    while(t--){
        int n, m; cin>>n>>m;
        if(n%2!=0 || m%2!=0){
            cout<<-1<<endl;
            continue;
        }
        cout<<n*m-1<<endl;
        auto solve=[&](auto solve, int i)->void{
            if(n==2*i || m==2*i) return;
            if(i&1){
                for(int j=0; j<(m-2*i)/2; j++){
                    cout<<n-i<<" "<<m-1-i-2*j<<endl;
                    cout<<n+1-i<<" "<<m-2-i-2*j<<endl;
                    cout<<n+1-i<<" "<<m-1-i-2*j<<endl;
                    cout<<n-i<<" "<<m-2-i-2*j<<endl;
                }
                for(int j=0; j<(n-2-2*i)/2; j++){
                    if(j==(n-2-2*i)/2-1){
                        cout<<n-1-i-2*j<<" "<<i<<endl;
                        cout<<n-2-i-2*j<<" "<<i+1<<endl;
                        cout<<n-2-i-2*j<<" "<<i<<endl;
                        cout<<n-1-i-2*j<<" "<<i+1<<endl;
                    }else{
                        cout<<n-1-i-2*j<<" "<<i<<endl;
                        cout<<n-2-i-2*j<<" "<<i+1<<endl;
                        cout<<n-1-i-2*j<<" "<<i+1<<endl;
                        cout<<n-2-i-2*j<<" "<<i<<endl;
                    }
                }
            }else{
                for(int j=0; j<(m-2*i)/2; j++){
                    cout<<i+2<<" "<<i+1+2*j<<endl;
                    cout<<i+1<<" "<<i+2+2*j<<endl;
                    cout<<i+1<<" "<<i+1+2*j<<endl;
                    cout<<i+2<<" "<<i+2+2*j<<endl;
                }
                for(int j=0; j<(n-2-2*i)/2; j++){
                    if(j==(n-2-2*i)/2-1){
                        cout<<i+3+2*j<<" "<<m-i<<endl;
                        cout<<i+4+2*j<<" "<<m-i-1<<endl;
                        cout<<i+4+2*j<<" "<<m-i<<endl;
                        cout<<i+3+2*j<<" "<<m-i-1<<endl;
                    }else{
                        cout<<i+3+2*j<<" "<<m-i<<endl;
                        cout<<i+4+2*j<<" "<<m-i-1<<endl;
                        cout<<i+3+2*j<<" "<<m-i-1<<endl;
                        cout<<i+4+2*j<<" "<<m-i<<endl;
                    }
                }
            }
            solve(solve, i+1);
        };
        solve(solve, 0);
    }
    return 0;
}