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 num[30];
string s;
int check(char c) {
  for (int i = 'a'; i < c; i++) {
    if (num[i]) {
      return 0;
    }
  }
  return 1;
}
stack<char> q;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cin >> s;
  for (int i = 0; i < s.size(); i++) {
    num[s[i]]++;
  }
  int cnt = 0;
  while (cnt < s.size()) {
    if (q.empty()) {
      q.push(s[cnt]);
      num[s[cnt]]--;
      cnt++;
    } else if (check(q.top())) {
      cout << q.top();
      q.pop();
    } else {
      q.push(s[cnt]);
      num[s[cnt]]--;
      cnt++;
    }
  }
  while (!q.empty()) {
    cout << q.top();
    q.pop();
  }
  return 0;
}
