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;
bool check(map<char, int> mpp, char ch) {
  for (auto i : mpp) {
    if (i.first < ch && i.second > 0) return true;
  }
  return false;
}
int main() {
  string a;
  cin >> a;
  int n = a.size();
  map<char, int> mp;
  for (int i = 0; i < n; i++) {
    mp[a[i]]++;
  }
  string ans = "";
  stack<char> t;
  t.push(a[0]);
  mp[a[0]]--;
  int i = 1;
  while (i < n) {
    if (t.empty() || check(mp, t.top())) {
      t.push(a[i]);
      mp[a[i]]--;
      i++;
    } else {
      while (!t.empty() && !check(mp, t.top())) {
        ans += t.top();
        t.pop();
      }
    }
  }
  while (!t.empty()) {
    ans += t.top();
    t.pop();
  }
  cout << ans << "\n";
  return 0;
}
