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;
char mins[100005];
int main() {
  string str;
  cin >> str;
  for (int i = 0; i < 100005; i++) {
    mins[i] = (char)((int)'z' + 1);
  }
  int n = str.length();
  for (int i = n - 1; i >= 0; i--) {
    mins[i] = min(mins[i + 1], str[i]);
  }
  string ans = "";
  stack<char> S;
  for (int i = 0; i < str.length(); i++) {
    if (S.size() == 0) {
      S.push(str[i]);
    } else {
      while (S.size() != 0 && S.top() <= mins[i]) {
        ans += S.top();
        S.pop();
      }
      S.push(str[i]);
    }
  }
  while (S.size() != 0) {
    ans += S.top();
    S.pop();
  }
  cout << ans;
}
