#include<iostream>
using namespace std;
int T,N,M;
main()
{
	cin>>T;
	for(;T--;)
	{
		cin>>N>>M;
		if(N%2!=0||M%2!=0)
		{
			cout<<-1<<endl;
			continue;
		}
		cout<<N*M-1<<endl;
		for(int j=1;j<M;j+=2)
		{
			if(j/2%2==0)
			{
				for(int i=1;i+2<N;i+=2)
				{
					cout<<i<<" "<<j<<endl;
					cout<<i+1<<" "<<j+1<<endl;
					cout<<i<<" "<<j+1<<endl;
					cout<<i+1<<" "<<j<<endl;
				}
				cout<<N-1<<" "<<j<<endl;
				cout<<N<<" "<<j+1<<endl;
				cout<<N<<" "<<j<<endl;
				cout<<N-1<<" "<<j+1<<endl;
			}
			else
			{
				cout<<N-1<<" "<<j<<endl;
				cout<<N<<" "<<j+1<<endl;
				cout<<N<<" "<<j<<endl;
				cout<<N-1<<" "<<j+1<<endl;
				for(int i=N-3;i>0;i-=2)
				{
					cout<<i+1<<" "<<j+1<<endl;
					cout<<i<<" "<<j<<endl;
					cout<<i+1<<" "<<j<<endl;
					cout<<i<<" "<<j+1<<endl;
				}
			}
		}
	}
}