#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  scanf("%d", &n);
  char t[n + 1];
  scanf("%s", t);
  int i = 0, k = 1;
  while (t[i] != '\0') {
    printf("%c", t[i]);
    i = i + k;
    k++;
  }
  return 0;
}
