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;
const int maxn = 1e5 + 10;
char str[maxn];
int vis[255];
int main() {
  cin >> str;
  int len = strlen(str);
  for (int i = 0; i < len; i++) {
    vis[str[i]]++;
  }
  int now = 'a';
  stack<char> sta;
  for (int i = 0; i < len; i++) {
    vis[str[i]]--;
    if (str[i] == now)
      cout << str[i];
    else
      sta.push(str[i]);
    while (vis[now] == 0) now++;
    while (!sta.empty() && sta.top() <= now) {
      cout << sta.top();
      sta.pop();
    }
  }
  while (!sta.empty()) {
    cout << sta.top();
    sta.pop();
  }
  cout << endl;
  return 0;
}
