#include <iostream>
#include <string>
#include <stdexcept>

using namespace std;

string decrypt_snakey(string encrypted, int col) {
    string decrypted;
    for (int i = 0; i < col; i++) {
        for (int offset = 0;; offset++) {
            try {
                decrypted += encrypted.at(i + offset * 2 * col);
                decrypted += encrypted.at((offset + 1) * 2 * col - i - 1);
            } catch (out_of_range&) {
                break;
            }
        }
    }
    return decrypted;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    string encrypted;
    int col;
    cin >> col >> encrypted;
    cout << decrypt_snakey(encrypted, col) << endl;

    return 0;
}