#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  string t;
  char a[100];
  cin >> t;
  a[0] = t[0];
  int i, j, k;
  for (i = 1, j = 0, k = 2; j < n; ++i, ++k) {
    j = j + k;
    a[i] = t[j];
  }
  a[i - 1] = '\0';
  cout << a;
  return 0;
}
