#include<bits/stdc++.h>

using namespace std;

int main()
{
	ios::sync_with_stdio(false);
	int T;cin>>T;
	while(T--)
	{
		int l,r;cin>>l>>r;
		if(l==r)cout<<"-1\n";
		else if((r-l)%2==0&&l%2==0)cout<<"-1\n";
		else
		{
			int now=l;
			while(now+2<r)
			{
				cout<<now+1<<' '<<now<<' ';
				now+=2;
			}
			if(now+2==r)cout<<now+1<<' '<<now+2<<' '<<now<<"\n";
			else cout<<now+1<<' '<<now<<"\n";
		}
	}
	return 0;
}