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(0);
  cin.tie(0);
  cout.tie(0);
  string s;
  cin >> s;
  vector<pair<char, int> > aux;
  for (int i = 0; i < s.size(); i++) {
    aux.push_back(make_pair(s[i], i));
  }
  sort(aux.begin(), aux.end());
  string ans = "";
  vector<int> taked;
  stack<char> help;
  int lastp = -1;
  for (int i = 0; i < aux.size(); i++) {
    if (aux[i].second > lastp) {
      if (!help.empty() && aux[i].first >= help.top()) {
        ans += help.top();
        help.pop();
        i--;
        continue;
      } else {
        ans += aux[i].first;
        for (int j = lastp + 1; j < aux[i].second; j++) help.push(s[j]);
        lastp = aux[i].second;
      }
    }
  }
  while (!help.empty()) {
    ans += help.top();
    help.pop();
  }
  cout << ans;
  return 0;
}
