#include <bits/stdc++.h>
using namespace std;
long long a[500009], b[500009];
map<long long, long long> mp;
vector<long long> vc;
int main() {
  cin.sync_with_stdio(false);
  long long i, j, k, l, c, v, n, m, r, t;
  long long x, x2, y1, y2, x3;
  string s, s1, s2, s3;
  while (cin >> n) {
    cin >> s;
    s1 = "";
    for (i = 0, j = 1; i < n; i += j) {
      s1 += s[i];
      j++;
    }
    cout << s1;
  }
}
