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;
int main() {
  string s;
  cin >> s;
  string p = s;
  sort(p.begin(), p.end());
  stack<char> stk;
  string ans = "";
  long long j = 0;
  long long i;
  long long k = 0;
  int f = 0;
  char next = 'a';
  i = 0;
  long long b[26] = {0};
  for (i = 0; i < s.length(); i++) {
    b[(s[i] - 'a')]++;
  }
  i = 0;
  while (i < s.length()) {
    for (k = 0; k < 26; k++) {
      if (b[k] != 0) {
        next = char('a' + k);
        break;
      }
    }
    while (!stk.empty() && stk.top() <= next) {
      ans += stk.top();
      stk.pop();
    }
    while (i < s.length()) {
      b[s[i] - 'a']--;
      if (next == s[i]) {
        ans += s[i];
        i++;
        break;
      } else {
        stk.push(s[i]);
      }
      i++;
    }
  }
  while (!stk.empty()) {
    ans += stk.top();
    stk.pop();
  }
  cout << ans << "\n";
}
