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() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  string str;
  cin >> str;
  stack<char> stk;
  map<char, long long int> mp;
  for (auto it : str) mp[it]++;
  char ch = 'a';
  string ans = "";
  for (long long int i = 0; i < str.length(); i++) {
    while (!mp[ch]) ch++;
    while (!stk.empty()) {
      if (stk.top() <= ch)
        ans += stk.top(), stk.pop();
      else
        break;
    }
    if (str[i] == ch)
      ans += ch;
    else
      stk.push(str[i]);
    mp[str[i]]--;
  }
  while (!stk.empty()) ans += stk.top(), stk.pop();
  cout << ans << '\n';
  return 0;
}
