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;
string s;
map<int, int> mp;
bool blz(char t) {
  for (int i = 0; i < t - 'a'; i++) {
    if (mp['a' + i] > 0) return true;
  }
  return false;
}
int main() {
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  cin >> s;
  stack<char> l;
  for (auto c : s) {
    mp[c]++;
  }
  string ans;
  for (int i = 0; i < s.size(); i++) {
    while (!l.empty() && !blz(l.top())) {
      ans += l.top();
      l.pop();
    }
    l.push(s[i]);
    mp[s[i]]--;
  }
  while (!l.empty()) {
    ans += l.top();
    l.pop();
  }
  cout << ans << '\n';
  return 0;
}
