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;
bool can(char c, int *a) {
  for (long long i = 0; i < int(c); i++) {
    if (a[i] > 0) return false;
  }
  return true;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(NULL);
  string s;
  cin >> s;
  stack<char> t1;
  string u;
  int a[256] = {0};
  for (long long i = 0; i < s.length(); i++) {
    a[s[i]]++;
  }
  for (long long i = 0; i < s.length(); i++) {
    while (!t1.empty() && can(t1.top(), a)) {
      u.push_back(t1.top());
      t1.pop();
    }
    t1.push(s[i]);
    a[s[i]]--;
  }
  while (t1.empty() == false) {
    u.push_back(t1.top());
    t1.pop();
  }
  cout << u;
  return 0;
}
