#include <bits/stdc++.h>
using namespace std;
int main() {
  long long t;
  cin >> t;
  string s;
  cin >> s;
  long long j = 1;
  string ans = "";
  long long k = 0;
  for (long long i = 0; i < s.length(); i++) {
    ans += s[i];
    i = i + k;
    k++;
  }
  cout << ans << endl;
}
