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 power(long long num, long long g, long long mod) {
  if (g == 0) return 1;
  if (g % 2 == 1) return (num * power((num * num) % mod, g / 2, mod)) % mod;
  return power((num * num) % mod, g / 2, mod);
}
int main() {
  string s;
  cin >> s;
  int a[26];
  memset(a, 0, sizeof(a));
  stack<char> t;
  string ans = "";
  for (auto x : s) a[x - 'a']++;
  for (auto x : s) {
    a[x - 'a']--;
    t.push(x);
    while (!t.empty()) {
      int val = t.top() - 'a';
      bool ok = true;
      for (int i = 0; i < val; i++) {
        if (a[i] != 0) ok = false;
      }
      if (!ok) break;
      ans += t.top();
      t.pop();
    }
  }
  cout << ans;
}
