#include <bits/stdc++.h>

using namespace std;

int k;
string s;
map<int, int> cnt;
vector<vector<char>> de_use;

int32_t main()
{
    cin >> k;
    de_use.resize(k + 1);
    getchar();
    getline(cin, s);
    int now = (int)s.size() - 1;
    cnt[1] ++;
    while(now > 0)
    {
        for(int i = 2; i <= k; i++)
            if(now-- > 0)
                cnt[i] ++;
        for(int i = k - 1; i > 0; i --)
            if(now-- > 0)
                cnt[i]++;
    }
    now = 0;
    for(int i = 1; i <= k; i++)
    {
        int new_ind = now + cnt[i];
        while(now != new_ind)
            de_use[i].push_back(s[now++]);
    }
    for(int i = 1; i <= k; i++)
        reverse(de_use[i].begin(), de_use[i].end());
    cout << de_use[1][--cnt[1]];
    de_use[1].pop_back();
    bool can = true;
    while(can)
    {
        for(int i = 2; i <= k; i++)
        {
            if(!de_use[i].empty())
            {
                cout << de_use[i][--cnt[i]];
                de_use[i].pop_back();
            }
            else
                can = false;
        }
        for(int i = k - 1; i > 0; i--)
        {
            if(!de_use[i].empty())
            {
                cout << de_use[i][--cnt[i]];
                de_use[i].pop_back();
            }
            else
                can = false;
        }
    }
}