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 s, ans;
int nxt[26][100005];
int main() {
  cin >> s;
  int i, j;
  for (i = 0; i < 26; i++) nxt[i][s.size()] = -1;
  for (i = s.size() - 1; i >= 0; i--) {
    for (j = 0; j < 26; j++) nxt[j][i] = nxt[j][i + 1];
    nxt[s[i] - 'a'][i] = i;
  }
  int cur = 0;
  stack<char> ss;
  for (i = 0; i < 26; i++) {
    while (ss.size() && ss.top() <= i + 'a') {
      ans += ss.top();
      ss.pop();
    }
    for (j = cur; j < s.size(); j++) {
      if (nxt[i][j] == -1) break;
      if (s[j] - 'a' == i)
        ans += s[j];
      else
        ss.push(s[j]);
    }
    cur = j;
  }
  while (ss.size()) {
    ans += ss.top();
    ss.pop();
  }
  cout << ans << endl;
}
