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 main() {
  string s;
  cin >> s;
  long long int a[26] = {0}, c = 0, i, j, n = s.size();
  vector<char> t, u;
  char p = 'a';
  for (i = 0; i < n; i++) {
    a[s[i] - 97]++;
  }
  for (i = 0; i < n; i++) {
    if (c == 0) {
      for (j = p - 97; j < 26; j++) {
        if (a[j] != 0) {
          p = j + 97;
          c = a[j];
          break;
        }
      }
    }
    if (s[i] == p) {
      if (t.size() > 0) {
        long long int x = t[t.size() - 1], y = s[i], z = t.size();
        while (x <= p && z > 0) {
          cout << t[z - 1];
          z--;
          if (z > 0) {
            x = t[z - 1];
          }
        }
        t.resize(z);
      }
      cout << p;
      c--;
    } else if (t.size() != 0) {
      long long int x = t[t.size() - 1], y = s[i], z = t.size();
      while (x <= p && z > 0) {
        cout << t[z - 1];
        z--;
        if (z > 0) {
          x = t[z - 1];
        }
      }
      t.resize(z);
      t.push_back(s[i]);
    } else {
      t.push_back(s[i]);
    }
    a[s[i] - 97]--;
  }
  if (t.size() > 0) {
    for (i = t.size() - 1; i >= 0; i--) {
      cout << t[i];
    }
  }
}
