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;
string s;
int cnt[26];
stack<char> st;
int main() {
  cin >> s;
  for (int i = 0; i < s.length(); i++) {
    cnt[s[i] - 'a']++;
  }
  int index = 0;
  for (int i = 0; i < s.length(); i++) {
    cnt[s[i] - 'a']--;
    while (index < 26 && cnt[index] == 0) {
      index++;
    }
    if (index < s[i] - 'a')
      st.push(s[i]);
    else {
      while (!st.empty()) {
        if (st.top() > s[i]) break;
        cout << st.top();
        st.pop();
      }
      cout << s[i];
      while (!st.empty()) {
        if (st.top() > 'a' + index) break;
        cout << st.top();
        st.pop();
      }
    }
  }
  while (!st.empty()) {
    cout << st.top();
    st.pop();
  }
  cout << endl;
  return 0;
}
