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>
const int INF = 1e9 + 3123, MOD = 1e9, MAXN = 10000;
const long double EPS = 0.000000000001;
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  string s;
  cin >> s;
  int n = (long long int)s.size();
  int a[100003];
  map<int, int> res;
  for (int i = 0; i < (long long int)s.size(); i++) {
    a[i] = s[i] - 'a';
    res[a[i]]++;
  }
  vector<int> q;
  q.push_back(INF);
  vector<int> ans;
  int index = 0;
  while (index < n) {
    int mini = INF - 1;
    for (int j = 0; j < 26; j++) {
      if (res[j] > 0) {
        mini = j;
        break;
      }
    }
    while (mini >= q.back()) {
      cout << char(q.back() + 'a');
      q.pop_back();
    }
    while (index < n) {
      if (a[index] == mini) {
        res[mini]--;
        ans.push_back(mini);
        cout << char(mini + 'a');
        index++;
        break;
      }
      res[a[index]]--;
      q.push_back(a[index]);
      index++;
    }
  }
  int mini = INF - 1;
  while (mini > q.back()) {
    cout << char(q.back() + 'a');
    q.pop_back();
  }
  return 0;
}
