#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  vector<char> a;
  int k = 0;
  for (int i = 0; i < n; i++) {
    vector<char> t;
    int j;
    for (j = i; j <= i + k; j++) {
      t.push_back(s[i]);
    }
    k++;
    i = j;
    a.push_back(t[0]);
    t.clear();
  }
  for (int i = 0; i < a.size(); i++) cout << a[i];
}
