#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 7, inf = 1e9 + 7;
const long long INF = 1e18 + 7;
const int X[] = {1, -1, 0, 0};
const int Y[] = {0, 0, 1, -1};
string s;
int main() {
  cin >> s;
  if (s.size() % 2 == 1) {
    cout << s[s.size() / 2];
    int cur1 = s.size() / 2 - 1;
    int cur2 = s.size() / 2 + 1;
    while (cur1 >= 0) {
      cout << s[cur2];
      cout << s[cur1];
      --cur1;
      ++cur2;
    }
  } else {
    cout << s[s.size() / 2 - 1];
    int cur1 = s.size() / 2 - 2;
    int cur2 = s.size() / 2;
    while (cur1 >= 0) {
      cout << s[cur2];
      cout << s[cur1];
      --cur1;
      ++cur2;
    }
    cout << s[cur2];
  }
  return 0;
}
