#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  long long int t, i, ans = 0, n, c = 0, k = 0, index, pos;
  cin >> n;
  string s, temp;
  cin >> s;
  for (i = 0; s[i]; i += k) {
    temp += s[i];
    k++;
  }
  cout << temp << '\n';
}
