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;
long long fp(long long n, long long p) {
  if (p == 0) return 1;
  if (p == 1) return n;
  long long res;
  res = fp(n, p / 2);
  res = (res * res);
  if (p % 2) res = (res * n);
  return res;
}
int main() {
  ios::sync_with_stdio(0);
  ios_base::sync_with_stdio(0);
  cin.tie(0), cout.tie(0);
  string s;
  vector<char> a, b;
  cin >> s;
  char arr[int(s.size()) + 5];
  arr[int(s.size())] = 'z' + 1;
  for (int i = int(s.size()) - 1; i >= 0; i--) {
    arr[i] = min(arr[i + 1], s[i]);
  }
  for (int i = 0, j = 0; i < 2 * int(s.size()); i++) {
    if (int(a.size()) == 0)
      a.push_back(s[j]), j++;
    else if (a.back() <= arr[j])
      b.push_back(a.back()), a.pop_back();
    else
      a.push_back(s[j]), j++;
  }
  for (auto i : b) cout << i;
  cout << '\n';
  return 0;
}
