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 freq[26];
char nxt = 'a';
string ans, temp;
int main() {
  string s;
  cin >> s;
  for (int i = 0; i < s.size(); i++) freq[s[i] - 'a']++;
  reverse(s.begin(), s.end());
  int k = s.size();
  for (int i = 0; i < k; i++) {
    char a = s.back();
    s.pop_back();
    temp += a;
    freq[a - 'a']--;
    while (!freq[nxt - 'a']) nxt++;
    if (nxt == 'z' + 1) continue;
    while (!temp.empty() && temp.back() <= nxt) {
      ans += temp.back();
      temp.pop_back();
    }
  }
  while (temp.size()) {
    ans += temp.back();
    temp.pop_back();
  }
  cout << ans << endl;
}
