#include <bits/stdc++.h>
template <typename T>
T modpow(T base, T exp, T modulus) {
  base %= modulus;
  T result = 1;
  while (exp > 0) {
    if (exp & 1) result = (result * base) % modulus;
    base = (base * base) % modulus;
    exp >>= 1;
  }
  return result;
}
using namespace std;
void solve() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  int delta = 1;
  for (int i = 0; i < n; i += delta++) {
    cout << s[i];
  }
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.precision(10);
  int t = 1;
  for (int i = 0; i < t; i++) solve();
  return 0;
}
