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;
bool findLowest(vector<int> arr, int c) {
  for (int i = 0; i < c; ++i) {
    if (arr[i] > 0) {
      return true;
    }
  }
  return false;
}
int main() {
  string s;
  cin >> s;
  vector<int> vi(26);
  for (char ch : s) {
    vi[ch - 'a']++;
  }
  stack<char> st;
  int i = 0;
  string res = "";
  while (i < s.length()) {
    if (st.empty() || findLowest(vi, st.top() - 'a')) {
      st.push(s[i]);
      vi[s[i] - 'a']--;
      i++;
    } else {
      res += (st.top());
      st.pop();
    }
  }
  while (!st.empty()) {
    res += (st.top());
    st.pop();
  }
  cout << res << endl;
  return 0;
}
