#include<iostream>
#include<string>
#include<cstdio>
using namespace std;

int n,l,r,l1,r1,ok;
string s;

int main()
{
    freopen("code.in", "r", stdin);
	freopen("code.out", "w" , stdout);
    cin>>n>>s;
    l=0;r=n-1;
    for(int i=1;i<=n;i++)
    {
        if(s[l]<s[r]){cout<<s[l];l++;continue;}
        if(s[r]<s[l]){cout<<s[r];r--;continue;}
        l1=l;r1=r;ok=0;
        for(int j=1;;j++)
        {
            l1++;
            r1--;
            if(l1>=r1){ok=1;break;}
            if(s[l1]<s[r1]){ok=1;break;}
            if(s[r1]<s[l1]){ok=2;break;}
        }
        if(ok==1){cout<<s[l];l++;continue;}
        cout<<s[r];r--;
    }
    return 0;
}