#include <fstream>
using namespace std;
ifstream cin("spioni.in");
ofstream cout("spioni.out");
void solve(string s)
{
    /// base case
    if(s.length() <= 2)
    {
        cout << s;
        return;
    }
    ///generam cele doua stringuri.
    string a = "", b = "";
    for(int i = 0;i<s.length();i++)
    {
        if(i%2==0)
            a+=s[i];
        else b+=s[i];
    }
    /// procedam la fel pentru stringurile generate.
    solve(a);
    solve(b);
}
int main()
{
    char c; cin>>c; /// absolut inutil.
    string s; cin >> s;
    solve(s);
    return 0;
}