#include <bits/stdc++.h>
using namespace std;
int main() {
  char s[55];
  int n, i, m;
  cin >> n;
  for (i = 1; i <= n; i++) {
    cin >> s[i];
  }
  for (i = 1, m = 1; i <= n; i = i + m, m++) {
    cout << s[i];
  }
  return 0;
}
