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;
string s, res;
stack<int> S;
vector<pair<int, int> > tab;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cin >> s;
  for (int i = 0; i < s.size(); ++i) tab.push_back({s[i] - 'a', i});
  tab.push_back({30, s.size()});
  sort(tab.begin(), tab.end());
  int pt = 0;
  for (int i = 0; i < s.size(); ++i) {
    S.push(s[i] - 'a');
    while (i >= tab[pt].second) ++pt;
    while (!S.empty() && S.top() <= tab[pt].first) {
      char zn = S.top() + 'a';
      res += string(1, zn);
      S.pop();
    }
  }
  cout << res << '\n';
}
