Petya recieved a gift of a string s with length up to 105 characters for his birthday. He took two more empty strings t and u and decided to play a game. This game has two possible moves:

  * Extract the first character of s and append t with this character. 
  * Extract the last character of t and append u with this character. 



Petya wants to get strings s and t empty and string u lexicographically minimal.

You should write a program that will help Petya win the game.

Input

First line contains non-empty string s (1 ≤ |s| ≤ 105), consisting of lowercase English letters.

Output

Print resulting string u.

Examples

Input

cab


Output

abc


Input

acdb


Output

abdc
#include <bits/stdc++.h>
using namespace std;
template <typename T>
ostream &operator<<(ostream &cout, vector<T> &a) {
  for (size_t i = 0; i < a.size(); ++i) cout << a[i] << " ";
  return cout;
}
template <typename T>
ostream &operator<<(ostream &cout, vector<vector<T> > &a) {
  for (size_t i = 0; i < a.size(); ++i) cout << a[i] << endl;
  return cout;
}
int main() {
  ios_base::sync_with_stdio(0);
  string s, u, t;
  cin >> s;
  int a[26] = {0};
  int b[26] = {0};
  for (int i = 0; i < s.size(); ++i) {
    ++a[s[i] - 'a'];
    ++b[s[i] - 'a'];
  }
  int cur = 0;
  for (int i = 0; i < s.size(); ++i) {
    u.push_back(s[i]);
    --a[s[i] - 'a'];
    while (cur < 26 && a[cur] == 0) ++cur;
    while (u.size() && u[u.size() - 1] <= cur + 'a') {
      while (cur < 26 && a[cur] == 0) ++cur;
      t.push_back(u[u.size() - 1]);
      u.pop_back();
    }
  }
  reverse(u.begin(), u.end());
  cout << t << u << endl;
  return 0;
}
