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 cnt[26];
string s, t, u;
int main() {
  cin >> s;
  for (int i = 0; i < s.size(); i++) {
    cnt[s[i] - 97]++;
  }
  reverse(s.begin(), s.end());
  for (int i = 0; i < 26; i++) {
    while (!t.empty() and t.back() - 97 <= i) {
      u.push_back(t.back());
      t.pop_back();
    }
    while (cnt[i] != 0 and !s.empty()) {
      cnt[s.back() - 97]--;
      if (s.back() - 97 == i) {
        u.push_back(s.back());
        s.pop_back();
      } else {
        t.push_back(s.back());
        s.pop_back();
      }
    }
  }
  cout << u;
  return 0;
}
