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 chk(int a[], char x) {
  for (int i = 0; i < x - 'a'; i++)
    if (a[i] > 0) return 0;
  return 1;
}
int main() {
  string s;
  cin >> s;
  int n = s.length();
  int a[26];
  memset(a, 0, sizeof(a));
  for (int i = 0; i < n; i++) {
    a[s[i] - 'a']++;
  }
  int c = 0;
  while (c < 26) {
    if (a[c] > 0) {
      break;
    }
    c++;
  }
  stack<char> t;
  string ans = "";
  int k = 0;
  while (k < n) {
    if (!t.empty() && chk(a, t.top())) {
      ans.push_back(t.top());
      t.pop();
    } else if (chk(a, s[k])) {
      ans.push_back(s[k]);
      a[s[k] - 'a']--;
      k++;
    } else {
      t.push(s[k]);
      a[s[k++] - 'a']--;
    }
  }
  while (!t.empty()) {
    ans.push_back(t.top());
    t.pop();
  }
  cout << ans << endl;
  return 0;
}
