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;
bool bit[100100];
stack<char> stk;
unordered_map<char, int> mp;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  int n, i, f;
  string s, u = "";
  char x, p;
  cin >> s;
  n = s.length();
  for (i = 0; i < n; i++) mp[s[i]]++;
  for (i = 0; i < n; i++) {
    p = s[i];
    f = 0;
    stk.push(p);
    mp[p]--;
    while (true) {
      if (stk.empty()) break;
      p = stk.top();
      f = 0;
      for (x = 'a'; x < p; x++) {
        if (mp[x] != 0) f = 1;
      }
      if (f == 1)
        break;
      else {
        u.push_back(p);
        stk.pop();
      }
    }
  }
  while (!stk.empty()) {
    p = stk.top();
    stk.pop();
    u.push_back(p);
  }
  cout << u;
  return 0;
}
