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() {
  string s;
  cin >> s;
  int l = s.length();
  int mark[26] = {0};
  for (int i = 0; i < l; i++) {
    mark[s[i] - 'a']++;
  }
  int j = 0;
  stack<char> st;
  for (int i = 0; i < l; i++) {
    while (j < 26 && mark[j] == 0) j++;
    while (!st.empty() && st.top() <= j + 'a') {
      printf("%c", st.top());
      st.pop();
    }
    if (j + 'a' == s[i]) {
      printf("%c", s[i]);
      mark[s[i] - 'a']--;
    } else {
      while (!st.empty() && st.top() <= j + 'a') {
        printf("%c", st.top());
        st.pop();
      }
      st.push(s[i]);
      mark[s[i] - 'a']--;
      while (!st.empty() && st.top() <= j + 'a') {
        printf("%c", st.top());
        st.pop();
      }
    }
  }
  while (!st.empty()) {
    printf("%c", st.top());
    st.pop();
  }
}
