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>
#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
#pragma GCC optimization("unroll-loops")
using namespace std;
const int maxn = 300001;
int cnt[26];
bool check(char ch) {
  int j = ch - 'a';
  for (int i = 0; i < j; i++) {
    if (cnt[i]) return 0;
  }
  return 1;
}
int main() {
  long long i, j, k, l, m, n;
  string s;
  cin >> s;
  n = s.length();
  for (i = 0; i < n; i++) {
    cnt[s[i] - 'a']++;
  }
  vector<char> v;
  i = 0;
  string r;
  while (i < n) {
    v.push_back(s[i]);
    cnt[s[i] - 'a']--;
    while (!v.empty() && check(v.back())) {
      r += v.back();
      v.pop_back();
    }
    i++;
  }
  while (v.size()) {
    r += v.back();
    v.pop_back();
  }
  cout << r;
}
