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() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  ;
  string str;
  cin >> str;
  long long int n = str.length();
  char suff[n];
  suff[n - 1] = str[n - 1];
  for (long long int i = n - 2; i >= 0; i--) {
    suff[i] = min(str[i], suff[i + 1]);
  }
  stack<char> s;
  long long int ptr = 0;
  for (long long int i = 0; i < n; i++) {
    if (ptr >= n) {
      cout << s.top();
      s.pop();
    } else if (!s.empty() && s.top() <= suff[ptr]) {
      cout << s.top();
      s.pop();
    } else {
      while (ptr < n && str[ptr] != suff[ptr]) {
        s.push(str[ptr++]);
      }
      cout << str[ptr];
      ptr++;
    }
  }
  cout << "\n";
  return 0;
}
