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() {
  string s;
  cin >> s;
  int n = s.length();
  int pres[200] = {0};
  for (int i = 0; i < n; i++) {
    pres[s[i]]++;
  }
  char alpha = 'a';
  while (pres[alpha] == 0 && alpha <= 'z') {
    alpha++;
  }
  string res = "";
  stack<char> ss;
  for (int i = 0; i < n; i++) {
    pres[s[i]]--;
    if (s[i] == alpha) {
      res += s[i];
      while (pres[alpha] == 0 && alpha <= 'z') {
        alpha++;
      }
      while (!ss.empty() && ss.top() <= alpha) {
        res += ss.top();
        ss.pop();
      }
    } else {
      ss.push(s[i]);
    }
  }
  while (!ss.empty()) {
    res += ss.top();
    ss.pop();
  }
  cout << res << endl;
  return 0;
}
