WA on #12,14,15,16,17,18,19,20

#include<bits/stdc++.h>
using namespace std;
int n;
unsigned long long k;
bool a[66];
int main(){
	cin>>n>>k;
	for(int i=1;i<=n;i++){
		int p=n-i+1;
		unsigned long long k1=1<<(i+1),k2a=1<<(i-1);
		unsigned long long k2b=3*(1<<(i-1))-1;
		int k3=k%k1;
		if(k3>=k2a&&k3<=k2b) a[p]=1;
		else a[p]=0;
	}
	for(int i=1;i<=n;i++){
		cout<<a[i];
	}
	return 0;
}