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;
const int N = 1e5 + 100;
char s[N], t[N];
int alp[26];
char findsmall() {
  for (int i = 0; i < 26; i++)
    if (alp[i]) return 'a' + i;
  return '-';
}
int out[26];
char findoutsmall() {
  for (int i = 0; i < 26; i++)
    if (out[i]) return 'a' + i;
  return '-';
}
int main() {
  int i, len;
  scanf("%s", s);
  len = strlen(s);
  memset(alp, 0, sizeof(alp));
  for (i = 0; i < len; i++) {
    out[s[i] - 'a']++;
  }
  stack<char> fin;
  char smallest;
  for (i = 0; i < len; i++) {
    smallest = findoutsmall();
    if (smallest == '-') break;
    while (!fin.empty() && fin.top() <= smallest) {
      cout << fin.top();
      out[fin.top()]--;
      fin.pop();
    }
    while (s[i] != smallest && i < len) {
      fin.push(s[i]);
      out[s[i] - 'a']--;
      i++;
    }
    if (i < len && s[i] == smallest) {
      putchar(s[i]);
      out[s[i] - 'a']--;
    }
  }
  while (!fin.empty()) {
    cout << fin.top();
    fin.pop();
  }
  return 0;
}
