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() {
  stack<char> st;
  string s;
  queue<int> pos[26];
  vector<int> p;
  cin >> s;
  s = s + 'z';
  int n = s.size();
  for (int i = 0; i < n; i++) {
    pos[(s[i] - 'a')].push(i);
  }
  int mx = -1;
  for (int i = 0; i < 26; i++) {
    while (!pos[i].empty()) {
      if (pos[i].front() > mx) {
        p.push_back(pos[i].front());
        mx = pos[i].front();
      }
      pos[i].pop();
    }
  }
  int j = 0;
  for (int i = 0; i < n - 1; i++) {
    if (i == p[j]) {
      cout << s[i];
      j++;
      while (!st.empty()) {
        if (st.top() <= s[p[j]]) {
          cout << st.top();
          st.pop();
        } else
          break;
      }
    } else
      st.push(s[i]);
  }
  while (!st.empty()) {
    cout << st.top();
    st.pop();
  }
  cout << endl;
  return 0;
}
