#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, l = 0, j;
  cin >> n;
  string s;
  cin >> s;
  string a[n];
  for (j = 0; j < n; j++) {
    cout << s[j];
    if (n == 1) {
      break;
    }
    l++;
    j = j + l;
  }
  cout << "\n";
}
