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;
map<char, int> mp;
char s[100005], ch = 'a';
int main() {
  int i, n, k, j;
  cin >> s;
  n = strlen(s);
  for (i = 0; i < n; i++) mp[s[i]]++;
  for (i = 0; i < n; i++) {
    while (mp[ch] == 0 && ch <= 'z') ch++;
    mp[s[i]]--;
    if (ch == s[i]) cout << s[i], s[i] = '1';
    if (mp[ch] == 0) {
      while (mp[ch] == 0 && ch <= 'z') ch++;
      for (k = i - 1; k >= 0; k--) {
        if (s[k] <= ch && s[k] != '1')
          cout << s[k], s[k] = '1';
        else if (s[k] != '1')
          break;
      }
    }
  }
  for (i = n - 1; i >= 0; i--)
    if (s[i] != '1') cout << s[i];
  return 0;
}
