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, t, u;
int d[1000];
int main() {
  cin >> s;
  t.resize(s.length());
  u = "";
  for (int i = 0; i < s.size(); ++i) ++d[s[i]];
  char x = 'a';
  int y = -1;
  for (int i = 0; i < s.size(); ++i) {
    while (x < 'z' && d[x] == 0) ++x;
    while (y >= 0 && t[y] <= x) {
      u.push_back(t[y]);
      --y;
    }
    if (s[i] == x) {
      u.push_back(s[i]);
      --d[x];
    } else {
      ++y;
      t[y] = s[i];
      --d[s[i]];
    }
  }
  while (y >= 0) u += t[y], --y;
  cout << u;
  return 0;
}
