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;
int main() {
  stack<char> s;
  map<char, int> mapp;
  cin.sync_with_stdio(false);
  string str;
  while (cin >> str) {
    mapp.clear();
    for (int i = 0; i < str.length(); i++) {
      mapp[str[i]]++;
    }
    map<char, int>::iterator it, ite;
    for (int i = 0; i < str.length(); i++) {
      it = mapp.begin();
      if (it->first == str[i]) {
        cout << str[i];
        it->second--;
        if (it->second == 0) {
          ite = it;
          it++;
          mapp.erase(ite);
          if (it == mapp.end()) {
            continue;
          }
          while (s.size() && s.top() <= (it->first)) {
            cout << s.top();
            s.pop();
          }
        }
      } else {
        s.push(str[i]);
        mapp[str[i]]--;
        if (mapp[str[i]] == 0) {
          mapp.erase(mapp.find(str[i]));
        }
      }
    }
    while (s.size()) {
      cout << s.top();
      s.pop();
    }
    cout << endl;
  }
  return 0;
}
