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;
  string u;
  int j = 0;
  int n = s.size();
  int cnt[26];
  memset(cnt, 0, sizeof(cnt));
  for (int i = 0; i < n; i++) {
    cnt[s[i] - 97]++;
  }
  stack<char> stk;
  for (int i = 0; i < 26; i++) {
    while (!stk.empty() && stk.top() <= i + 97) {
      u += stk.top();
      stk.pop();
    }
    for (; j < n && cnt[i]; j++) {
      if (s[j] == i + 97)
        u += s[j];
      else
        stk.push(s[j]);
      cnt[s[j] - 97]--;
    }
  }
  while (!stk.empty()) {
    u += stk.top();
    stk.pop();
  }
  cout << u << endl;
}
