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;
char s[100100];
int n;
char ans[100100];
int siz;
int cnt[30];
char sta[100100];
int ss;
int main() {
  scanf("%s", s);
  n = strlen(s);
  int las = 0;
  for (int i = 0; i < n; ++i) ++cnt[s[i] - 'a'];
  int now = 0;
  siz = ss = 0;
  for (int i = 0; i < n; ++i) {
    while (now < 26 && cnt[now] == 0) now++;
    if (s[i] - 'a' != now) {
      sta[ss++] = s[i];
      --cnt[s[i] - 'a'];
      continue;
    }
    ans[siz++] = s[i];
    --cnt[now];
    while (now < 26 && cnt[now] == 0) ++now;
    while (ss > 0 && sta[ss - 1] - 'a' <= now) {
      ans[siz++] = sta[ss - 1];
      ss--;
    }
  }
  while (ss > 0) {
    ans[siz++] = sta[ss - 1];
    ss--;
  }
  ans[siz++] = 0;
  printf("%s\n", ans);
  return 0;
}
