#include <bits/stdc++.h>
using namespace std;
int main() {
  string A;
  cin >> A;
  if (A.size() > 1 and A.size() % 2 == 0) {
    int x = (A.size() / 2) - 1;
    cout << A[x];
    for (int i = 1; i <= x; i++) {
      cout << A[x + i] << A[x - i];
    }
    cout << A[2 * x + 1];
  } else if (A.size() % 2 != 0 and A.size() > 1) {
    int x = (A.size() / 2);
    cout << A[x];
    for (int i = 1; i <= x; i++) {
      cout << A[x + i] << A[x - i];
    }
  } else {
    cout << A[0];
  }
}
