#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  long long int n, ctr = 1;
  cin >> n;
  cin >> s;
  for (long long int i = 0; i < n;) {
    cout << s[i];
    if (i == 0) {
      i += 1;
    } else {
      i += ctr + 1;
    }
    ctr++;
  }
  return 0;
}
