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;
unsigned long symbs[30];
vector<char> mystack;
bool is_top_min() {
  for (size_t i = 0; i < (mystack[0] - 'a'); i++)
    if (symbs[i] > 0) return false;
  return true;
}
int main(int argc, char *argv[]) {
  string s;
  string u;
  memset(symbs, 0, sizeof(unsigned long) * 30);
  cin >> s;
  for (const auto &sym : s) symbs[sym - 'a']++;
  for (const auto &sym : s) {
    mystack.insert(mystack.begin(), sym);
    symbs[sym - 'a']--;
    while (mystack.size() > 0 && is_top_min()) {
      u.push_back(mystack[0]);
      mystack.erase(mystack.begin());
    }
  }
  for (size_t i = 0; i < mystack.size(); i++) u.push_back(mystack[i]);
  cout << u;
  return 0;
}
