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;
long long binpow(long long a, long long b) {
  long long res = 1;
  while (b > 0) {
    if (b & 1) res = res * a;
    a = a * a;
    b >>= 1;
  }
  return res;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  string s, finale = "";
  cin >> s;
  int count[26] = {0}, id = 0;
  for (int i = 0; i < s.length(); i++) count[s[i] - 97]++;
  stack<char> element;
  for (int i = 0; i < s.length(); i++) {
    if (count[id] == 0) {
      for (int i = id; i < 26; i++) {
        if (count[i] != 0) {
          id = i;
          break;
        }
      }
    }
    while (!element.empty() && element.top() <= 'a' + id) {
      cout << element.top();
      element.pop();
    }
    element.push(s[i]);
    count[s[i] - 97]--;
  }
  int n = element.size();
  for (int i = 0; i < n; i++) {
    cout << element.top();
    element.pop();
  }
}
