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;
int freq[26];
char getMin() {
  for (int i = 0; i < 26; ++i) {
    if (freq[i] < 0) assert(false);
    if (freq[i] > 0) return i + 'a';
  }
  return -1;
}
void remove(char ch) { freq[ch - 'a']--; }
int main(int argc, char const *argv[]) {
  string s, t, u;
  cin >> s;
  memset(freq, 0, sizeof(freq));
  for (int i = 0; i < s.size(); ++i) freq[s[i] - 'a']++;
  for (int i = 0; i < s.size(); ++i) {
    char ch = s[i];
    t.push_back(ch);
    remove(ch);
    if (getMin() == -1) {
      while (t.size() != 0) {
        u.push_back(t[t.size() - 1]);
        t = t.substr(0, t.size() - 1);
      }
    }
    while (t.size() != 0 && getMin() >= t[t.size() - 1]) {
      u.push_back(t[t.size() - 1]);
      t = t.substr(0, t.size() - 1);
    }
  }
  cout << u << endl;
  return 0;
}
