#include <bits/stdc++.h>
using namespace std;
double a[1000010];

int main()
{
	freopen("changgao_real.in","r",stdin);
	freopen("changgao_real.out","w",stdout);
	double f;
	string s;
	cin>>f;
	cin>>s;
	if(s[0]=='1') a[1]=1;
	
	for(int i=1;i<s.size();i++)
	{
		if(s[i]=='1')
		{
			a[i+1]=a[i]+1;
		}
		else if(s[i]=='0')
		{
			a[i+1]=a[i];
		}
	}
	double c1=10,f1,l1=0,r1=0;
	for(int i=1;i<=s.size();i++)
	{
		for(int j=i;j<=s.size();j++)
		{
			double f2=(a[j+1]-a[i])/(j-i+1);
			double c2=f-f2;
			if(c2<0) c2=c2*(-1);
	//		cout<<f2<<" "<<c2<<" ";
			if(c2<c1)
			{
				f1=f2;
				l1=i;
				r1=j;
				c1=c2;
			}
	//		cout<<i<<" "<<j<<endl;
		}
	}
//	cout<<r1<<" "<<l1<<endl;
	int m=0;
	int k=1;
	for(int i=r1;i>=l1;i--)
	{
		if(s[i]=='1')
		{
			m=m+k;
		}
		k=k*2;
	}				
	cout<<m;
	return 0;
}