#include <bits/stdc++.h>
using namespace std;
const long long MAXN = 1e5 + 10;
const long long INF = 1e18;
const long long MOD = 1e9 + 7;
int main() {
  string s;
  cin >> s;
  long long n = s.size();
  long long o = (n - 1) / 2;
  string a = "", b = "";
  for (int i = o; i >= 0; i--) {
    a += s[i];
  }
  for (int i = o + 1; i < n; i++) {
    b += s[i];
  }
  for (int i = 0; i <= o; i++) {
    cout << a[i];
    if (b.size() > i) {
      cout << b[i];
    }
  }
}
