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 l[26];
int main() {
  string s;
  cin >> s;
  for (int i = 0; i < s.size(); i++) {
    l[s[i] - 'a']++;
  }
  vector<char> u;
  for (int i = 0; i < s.size(); i++) {
    char min;
    l[s[i] - 'a']--;
    for (int j = 0; j < 26; j++) {
      if (l[j]) {
        min = char(97 + j);
        break;
      }
    }
    u.push_back(s[i]);
    while (u.back() <= min && !u.empty()) {
      cout << u.back();
      u.pop_back();
    }
  }
  while (!u.empty()) {
    cout << u.back();
    u.pop_back();
  }
  cout << endl;
}
