#include <iostream>
#include <cstdio>
#include <algorithm>
#include <vector>
#include <string.h>
using namespace std;
typedef int lld;

char s[10002], build[10002];
lld len, sz=0;

int main ()
{
    freopen("code.in", "r", stdin);
    freopen("code.out", "w", stdout);

    lld p1, p2;

    scanf("%d", &len);
    scanf("%s", s);

    p1 = 0; p2 = len-1;
    while (p1 < p2)
    {
        if (s[p1] != s[p2])
        {
            if (s[p1] < s[p2])
            {
                build[++sz] = s[p1++];
            }
            else
            {
                build[++sz] = s[p2--];
            }
            continue;
        }

        char ns1='-', ns2;
        lld cnt1=0, cnt2=0, i1, i2;

        for (lld i=p1; i<p2; i++)
        {
            cnt1++;
            if (s[p1] == s[i]) continue;

            i1 = i;
            ns1 = s[i]; break;
        }

        if (ns1 == '-')
        {
            for (lld i=p1; i<=p2; i++)
            {
                build [++sz] = s[i];
            }
            p1 = p2+1;

            break;
        }

        for (lld i=p2; i>p1; i--)
        {
            cnt2++;
            if (s[p2] == s[i]) continue;

            i2 = i;
            ns2 = s[i]; break;
        }

        if (ns1 > s[p1] && ns2 > s[p2])
        {
            for (lld i=p1; i<i1; i++)
            {
                build[++sz] = s[i];
            }
            for (lld i=p2; i>i2; i--)
            {
                build[++sz] = s[i];
            }

            p1 = i1;
            p2 = i2;
            continue;
        }
        if (ns1 > s[p1])
        {
            for (lld i=p2; i>=i2; i--)
            {
                build[++sz] = s[i];
            }

            p2 = i2-1;
            continue;
        }
        if (ns2 > s[p2])
        {
            for (lld i=p1; i<=i1; i++)
            {
                build[++sz] = s[i];
            }

            p1 = i1+1;
            continue;
        }

        if (cnt1 < cnt2)
        {
            for (lld i=p1; i<=i1; i++)
            {
                build[++sz] = s[i];
            }

            p1 = i1+1;
            continue;
        }
        else if (cnt1 > cnt2)
        {
            for (lld i=p2; i>=i2; i--)
            {
                build[++sz] = s[i];
            }

            p2 = i2-1;
            continue;
        }
        else
        {
            if (ns1 < ns2)
            {
                for (lld i=p1; i<=i1; i++)
                {
                    build[++sz] = s[i];
                }

                p1 = i1+1;
                continue;
            }
            else if (ns1 > ns2)
            {
                for (lld i=p2; i>=i2; i--)
                {
                    build[++sz] = s[i];
                }

                p2 = i2-1;
                continue;
            }
            else
            {
                bool first;

                lld d1 = i1+1, d2 = i2-1;
                while (d1 < d2)
                {
                    if (s[d1] == s[d2])
                    {
                        d1++;
                        d2--;
                        continue;
                    }

                    first = (s[d1] < s[d2]);
                    break;
                }

                if (first)
                {
                    for (lld i=p1; i<=i1; i++)
                    {
                        build[++sz] = s[i];
                    }

                    p1 = i1+1;
                    continue;
                }
                else
                {
                    for (lld i=p2; i>=i2; i--)
                    {
                        build[++sz] = s[i];
                    }

                    p2 = i2-1;
                    continue;
                }
            }
        }
    }

    if (p1 == p2)
    {
        build[++sz] = s[p2];
    }

    for (lld i=1; i<=sz; i++)
    {
        printf("%c", build[i]);
    }
    printf("\n");
}