#include <stdio.h>
#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 10000000000000001


int main(){
	
	int N,K;
	cin>>N>>K;
	
	if((N+1)/2 <= K){
		string ans(N,'1');
		rep(i,K)ans[i] = '0';
		cout<<ans<<endl;
	}
	else{
		cout<<-1<<endl;
	}
	
	
	return 0;
}