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, ans = "";
  stack<char> st;
  int a[26] = {0};
  cin >> s;
  for (int i = 0; i < s.size(); i++) a[s[i] - 'a']++;
  for (int i = 0; i < s.size(); i++) {
    st.push(s[i]);
    a[s[i] - 'a']--;
    while (!st.empty()) {
      int flag = 1;
      for (int j = 0; j < st.top() - 'a'; j++) {
        if (a[j]) {
          flag = 0;
          break;
        }
      }
      if (flag) {
        ans += st.top();
        st.pop();
      } else {
        break;
      }
    }
  }
  while (!st.empty()) {
    ans += st.top();
    st.pop();
  }
  cout << ans;
}
