#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long i, j, n, m, k, cnt = 0, ans = 0, t = 1;
  string s;
  cin >> n;
  cin >> s;
  string out = "";
  cnt = 1;
  for (i = 0; i < s.length(); i++) {
    out += s[i];
    i += (cnt - 1);
    cnt++;
  }
  return cout << out, 0;
  return 0;
}
