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;
template <typename T>
void sci(T& t) {
  cin >> t;
}
template <typename T, typename... Ts>
void sci(T& t, Ts&... ts) {
  sci(t);
  sci(ts...);
}
template <typename T, typename Cmp = std::greater<T>>
using heap = priority_queue<T, std::vector<T>, Cmp>;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  multiset<char> s;
  string ts;
  sci(ts);
  int n = ts.length();
  for (char c : ts) {
    s.insert(c);
  }
  vector<char> t, u;
  int i = 0;
  while (!s.empty() || !t.empty()) {
    if (t.empty() || (!s.empty() && *s.begin() < t.back())) {
      t.push_back(ts[i]);
      s.erase(s.find(ts[i]));
      i++;
    } else {
      u.push_back(t.back());
      t.pop_back();
    }
  }
  for (char c : u) {
    cout << c;
  }
  return 0;
}
