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);
  string s;
  cin >> s;
  long long n = s.length();
  pair<long long, long long> util[n];
  util[n - 1] = make_pair(s[n - 1] - 'a', n - 1);
  for (long long i = n - 2; i >= 0; i--) {
    long long temp = s[i] - 'a';
    if (temp > util[i + 1].first) {
      util[i] = util[i + 1];
    } else {
      util[i] = make_pair(temp, i);
    }
  }
  deque<long long> dq;
  string u;
  long long idx = -1;
  while (u.length() < n) {
    if (dq.empty() || (idx + 1 < n && dq.back() > util[idx + 1].first)) {
      u += 'a' + (util[idx + 1].first);
      for (long long i = idx + 1; i < util[idx + 1].second; i++) {
        dq.push_back(s[i] - 'a');
      }
      idx = util[idx + 1].second;
    } else {
      u += 'a' + dq.back();
      dq.pop_back();
    }
  }
  cout << u << endl;
  return 0;
}
