#include<bits/stdc++.h>

using namespace std;



int t;

bool a[100050];



void chuli(int n,int p)

{

	int p1=n/2-1;

	//if()

	if((n%2==0&&p>p1) || (n%2!=0&&p>n/2))

		cout<<"-1";

	else

	{



	int i=1;



	while(i<=n)//for(int i=1;i<=n;i+2)

	{

		int i1=i+2;



		if(p>0)

		{

			p=p-1;

			a[i]=1;

			a[i1]=1;

			

		}

		

			i+=2;

		

	}

	for(int i=n;i>0;i--)

		cout<<a[i];

	}

	cout<<endl;



}



int main()

{



	cin>>t;

	for(int i=1;i<=t;i++)

	{

		int n,p;

		cin>>n>>p;

		chuli(n,p);

	}

	return 0;

}