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;
struct vars {
  int a, b;
};
int i, j, k;
void solve() {
  string s;
  cin >> s;
  stack<char> st;
  queue<char> qu;
  int a[26] = {0};
  for (int i = 0; i <= s.size() - 1; i++) {
    a[s[i] - 'a']++;
  }
  j = 0;
  for (int i = 0; i <= s.size() - 1; i++) {
    j = 0;
    while (j < 25) {
      if (a[j]) break;
      j++;
    }
    while (!st.empty() && st.top() <= ('a' + j)) {
      qu.push(st.top());
      st.pop();
    }
    if (s[i] != ('a' + j)) {
      st.push(s[i]);
    } else {
      qu.push(s[i]);
    }
    a[s[i] - 'a']--;
  }
  while (!st.empty()) {
    qu.push(st.top());
    st.pop();
  }
  while (!qu.empty()) {
    cout << qu.front();
    qu.pop();
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  solve();
  return 0;
}
