#include <bits/stdc++.h>
using namespace std;
bool isprime(int n) {
  for (int i = 2; i < n; i++) {
    if (n % i == 0) {
      return false;
    }
  }
  return true;
}
int main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  int diff = 1;
  int i = 0;
  while (i < n) {
    cout << s[i];
    i = i + diff;
    diff++;
  }
}
