#include<iostream>
using namespace std;
bool map[100005];
int main(){
	ios::sync_with_stdio(0);
	cin.tie(0),cout.tie(0);
	int t;
	cin>>t;
	while(t--){
		int n,p,ans=0;
		cin>>n>>p;
		double a=n*1.0;
		if(p>=a*1.0/2) cout<<-1;
		else{
			for(int i=n-1;i>=0;i--){
				if(p==1){
					map[n-1]=1;
					map[n-3]=1;
					break;
				}
				if(ans==p){
					map[i]=1;
					break;
				}
				if(n%2==1){
					if(i%2==0) map[i]=1;
					else map[i]=0,ans++;
				}else 
					if(i%2==1) map[i]=1;
					else map[i]=0,ans++;
				
			}
			for(int i=0;i<n;i++) cout<<map[i];
		}
		cout<<endl;
	}
	return 0;
}