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;
int32_t main() {
  string arr, ans_str = "";
  cin >> arr;
  long long freq[26] = {}, ptr = 0, n;
  stack<long long> s;
  n = arr.size();
  for (long long i = 0; i < n; i++) {
    freq[arr[i] - 97] += 1;
  }
  long long i = 0;
  while (freq[ptr] == 0) ptr++;
  while (i < n) {
    if (ptr == (arr[i] - 97)) {
      cout << arr[i];
      freq[ptr]--;
    } else {
      s.push(arr[i]);
      freq[arr[i] - 97]--;
    }
    while (freq[ptr] == 0 && ptr < 26) ptr++;
    while (!s.empty() && (ptr >= (char(s.top()) - 97))) {
      if (arr[i + 1] < char(s.top())) {
        break;
      }
      cout << char(s.top());
      s.pop();
      while (freq[ptr] == 0 && ptr < 26) ptr++;
    }
    i++;
  }
  while (!s.empty()) {
    cout << char(s.top());
    s.pop();
  }
  return 0;
}
