#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  string s;
  cin >> n;
  int a[n];
  cin >> s;
  int l = s.size();
  int i = 0, p = 0, c = 0;
  while (p < n) {
    p = p + c;
    a[i] = p;
    c++;
    i++;
  }
  for (int u = 0; u < i - 1; u++) {
    cout << s[a[u]];
  }
}
