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() {
  map<char, int> mp;
  map<long int, long int> result;
  map<long int, long int>::iterator itr;
  stack<char> ans;
  string str;
  int i;
  cin >> str;
  char c = 'a';
  for (i = 1; i <= 26; i++) {
    mp[c] = i;
    c++;
  }
  for (i = 0; i < str.size(); i++) {
    result[mp[str[i]]]++;
  }
  for (i = 0; i < str.size(); i++) {
    result[mp[str[i]]]--;
    if (result[mp[str[i]]] == 0) {
      result.erase(mp[str[i]]);
    }
    ans.push(str[i]);
    if (!result.empty()) {
      itr = result.begin();
      while (!ans.empty() && mp[ans.top()] <= itr->first) {
        cout << ans.top();
        ans.pop();
      }
    }
  }
  while (!ans.empty()) {
    cout << ans.top();
    ans.pop();
  }
}
