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 solve() {
  string s;
  cin >> s;
  long long n = (long long int)s.size();
  stack<char> t;
  string u;
  vector<long long int> pos(26, 0);
  for (long long int i = 0; i < n; i++) pos[s[i] - 'a']++;
  for (long long int i = 0; i < n; i++) {
    t.push(s[i]);
    pos[s[i] - 'a']--;
    while ((long long int)t.size()) {
      long long f = 0;
      for (long long int j = 0; j < (t.top() - 'a'); j++)
        if (pos[j]) f = 1;
      if (f == 0)
        u += t.top(), t.pop();
      else
        break;
    }
  }
  while ((long long int)t.size()) u += t.top(), t.pop();
  cout << u;
  return 0;
}
int main() {
  auto start = chrono::high_resolution_clock::now();
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long test_cases = 1;
  while (test_cases--) solve();
  auto stop = chrono::high_resolution_clock::now();
  auto duration = chrono::duration_cast<chrono::milliseconds>(stop - start);
}
