#include <bits/stdc++.h>
using namespace std;
int ceil(int a, int b) {
  if (a % b == 0)
    return a / b;
  else
    return a / b + 1;
}
const int MOD = 1e9 + 7;
int power(long long x, unsigned int y, int p) {
  int res = 1;
  x = x % p;
  if (x == 0) return 0;
  while (y > 0) {
    if (y & 1) res = (res * x) % p;
    y = y >> 1;
    x = (x * x) % p;
  }
  return res;
}
int main() {
  int t = 1;
  while (t) {
    int n;
    cin >> n;
    string s;
    cin >> s;
    for (int i = 0, j = 1; i < n;) {
      cout << s[i];
      j++;
      i += j;
    }
    t--;
  }
  return 0;
}
