#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, i, j = 0;
  cin >> n;
  char str[n];
  cin >> str;
  for (i = 0; str[i] != '\0'; i = i + j) {
    printf("%c", str[i]);
    j++;
  }
  printf("\n");
}
