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;
  long long n = s.size();
  map<char, long long> ms;
  map<char, long long> ma;
  for (long long i = 0; i < s.size(); i++) ms[s[i]]++;
  string a, b, x;
  long long i = 0;
  long long j = 0;
  while (b.size() < n) {
    auto it = ms.begin();
    if (it != ms.end() && (a.empty() || it->first < a.back())) {
      while (s[i] != it->first) {
        a.push_back(s[i]);
        ms[s[i]]--;
        if (ms[s[i]] == 0) ms.erase(s[i]);
        i++;
      }
      i++;
      ms[it->first]--;
      if (ms[it->first] == 0) ms.erase(it->first);
      b.push_back(it->first);
    } else {
      b.push_back(a.back());
      a.pop_back();
    }
  }
  cout << b << endl;
}
