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::sync_with_stdio(0);
  cin.tie(0);
  string s;
  cin >> s;
  vector<long long> count(26);
  stack<long long> t;
  vector<char> result;
  for (long long i = 0; i < s.size(); i++) {
    count[s[i] - 'a']++;
  }
  for (long long i = 0; i < s.size(); i++) {
    t.push(s[i]);
    count[t.top() - 'a']--;
    while (!t.empty()) {
      bool check = true;
      for (long long j = t.top() - 1 - 'a'; j > -1; j--) {
        if (count[j]) {
          check = false;
        }
      }
      if (!check) break;
      result.push_back(t.top());
      t.pop();
    }
  }
  while (!t.empty()) {
    result.push_back(t.top());
    t.pop();
  }
  for (long long i = 0; i < result.size(); i++) {
    cout << result[i];
  }
  cout << endl;
}
