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>
#pragma optimize("Ofast")
using namespace std;
using ll = long long;
const int N = 1e5 + 5;
int main() {
  ios_base::sync_with_stdio(0);
  string s;
  cin >> s;
  map<char, int> cnt;
  for (int i = 0; i < s.size(); ++i) {
    cnt[s[i]]++;
  }
  stack<char> stk;
  for (int i = 0; i < s.size(); ++i) {
    char ch = s[i];
    stk.push(ch);
    cnt[ch]--;
    while (stk.size()) {
      ch = stk.top();
      bool smaller = false;
      for (char itr = 'a'; itr < ch; ++itr) {
        if (cnt[itr]) {
          smaller = true;
        }
      }
      if (smaller == false) {
        cout << stk.top();
        stk.pop();
      } else {
        break;
      }
    }
  }
  while (stk.size()) {
    cout << stk.top();
    stk.pop();
  }
  return 0;
}
