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;
string s;
int ok[128] = {0};
stack<char> ss;
int main() {
  ios::sync_with_stdio(false);
  cin >> s;
  for (int i = 0; i < s.length(); i++) ok[s[i]] = 1;
  int now = 0;
  for (char i = 'a'; i <= 'z'; i++) {
    if (!ok[i]) continue;
    while (!ss.empty() && ss.top() <= i) {
      cout << ss.top();
      ss.pop();
    }
    int t = s.length() - 1;
    while (s[t] != i) t--;
    while (now <= t) {
      if (s[now] == i)
        cout << i;
      else
        ss.push(s[now]);
      now++;
    }
  }
  while (!ss.empty()) {
    cout << ss.top();
    ss.pop();
  }
  cout << endl;
  return 0;
}
