#include <bits/stdc++.h>
using namespace std;
const int N = 100;
char s[N];
int n, t = 0;
int main() {
  cin >> n;
  cin >> (s + 1);
  int i = 1;
  while (t < n) {
    char o;
    for (int j = 1; j <= i; j++) o = s[++t];
    putchar(o);
    ++i;
  }
  return 0;
}
