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 a[111111];
int main() {
  char s[111111];
  scanf("%s", s);
  int len = strlen(s);
  a[len + 1] = 1111;
  for (int i = len - 1; i >= 0; i--) {
    if (i == len - 1) {
      a[i + 1] = s[i] - 'a';
    } else {
      a[i + 1] = s[i] - 'a';
      if (a[i + 2] < a[i + 1]) a[i + 1] = a[i + 2];
    }
  }
  a[0] = 1111;
  string ans = "";
  stack<int> sta;
  sta.push(111);
  int lenn = 0;
  int now = 1;
  while (lenn != len) {
    while (sta.top() > a[now]) {
      sta.push(s[now - 1] - 'a');
      now++;
    }
    char c = sta.top();
    ans += char(sta.top() + 'a');
    sta.pop();
    lenn++;
  }
  cout << ans << endl;
}
