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 lexicalString(string s);
bool checkIfSmaller(char c, int arr[]);
int main() {
  string s;
  cin >> s;
  cout << lexicalString(s) << endl;
}
string lexicalString(string s) {
  stack<char> st;
  string ustring = "";
  int arr[27];
  for (int i = 0; i <= 26; ++i) arr[i] = 0;
  int l = s.length();
  for (int i = 0; i < l; ++i) {
    arr[s[i] - 'a']++;
  }
  for (int i = 0; i < l; ++i) {
    if (st.empty() || st.top() >= s[i]) {
      st.push(s[i]);
      arr[s[i] - 'a']--;
    } else {
      while (!st.empty() && checkIfSmaller(st.top(), arr)) {
        char top = st.top();
        st.pop();
        ustring += top;
      }
      st.push(s[i]);
      arr[s[i] - 'a']--;
    }
  }
  while (!st.empty()) {
    char top = st.top();
    st.pop();
    ustring += top;
  }
  return ustring;
}
bool checkIfSmaller(char c, int arr[]) {
  bool flag = true;
  for (int i = 0; i < c - 'a'; ++i) {
    if (arr[i] >= 1) {
      flag = false;
      break;
    }
  }
  if (flag) return true;
  return false;
}
