#include <bits/stdc++.h>
using namespace std;
long long int myXOR(unsigned long long int x, unsigned long long int y) {
  return (x | y) & (~x | ~y);
}
long long int powerLL(long long int x, long long int n) {
  long long int result = 1;
  while (n) {
    if (n & 1) result = result * x % 1000000007;
    n = n / 2;
    x = x * x % 1000000007;
  }
  return result;
}
int main() {
  long long int a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, t, u, w,
      x, y, z;
  string str, ss, str1;
  cin >> n;
  cin >> str;
  i = 1;
  long long int ind = 0;
  string res = "";
  while (ind < n) {
    res += std::string() + str[ind];
    ind += i;
    i++;
  }
  cout << res;
}
