#include <bits/stdc++.h>
using namespace std;
long long int n, m, y, steps;
char c;
string s, s1, s2;
int compare(const void* a, const void* b) { return ((*(int*)a) - (*(int*)b)); };
int main() {
  cin >> s;
  if (s.length() % 2) {
    steps = s.length();
    for (int i = 0; i < steps; i++) {
      if (!(i % 2)) {
        s1 += s[0];
        s.replace(0, 1, "");
      } else {
        s1 += s[s.length() - 1];
        s.replace(s.length() - 1, 1, "");
      }
    }
  } else {
    steps = s.length();
    for (int i = 0; i < steps; i++) {
      if ((i % 2)) {
        s1 += s[0];
        s.replace(0, 1, "");
      } else {
        s1 += s[s.length() - 1];
        s.replace(s.length() - 1, 1, "");
      }
    }
  }
  for (int i = s1.length() - 1; i >= 0; i--) {
    cout << s1[i];
  }
  return 0;
}
