#include <bits/stdc++.h>
using namespace std;
int a[100004];
int main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  int a = 1;
  int i = 2;
  vector<char> v;
  while (1) {
    if ((a - 1) >= s.size()) break;
    v.push_back(s[a - 1]);
    cout << s[a - 1];
    a = a + i;
    i++;
  }
  cout << endl;
}
