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 long long N = 150005, INF = (long long)1e9;
long double pi = 3.1415926535897932;
long long power(long long a, long long b, long long p) {
  if (a == 0) return 0;
  long long res = 1;
  a %= p;
  while (b > 0) {
    if (b & 1) res = (res * a) % p;
    b >>= 1;
    a = (a * a) % p;
  }
  return res;
}
int32_t main() {
  std::ios::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  cout.precision(std::numeric_limits<double>::max_digits10);
  ;
  string s;
  cin >> s;
  long long n = s.size();
  string ans = "";
  stack<char> second;
  long long r = 0;
  long long ch[n];
  ch[n - 1] = s[n - 1] - 'a';
  for (long long i = n - 2; i >= 0; i--)
    ch[i] = min(ch[i + 1], (long long)(s[i] - 'a'));
  for (long long i = 0; i < n; i++) {
    while (!second.empty()) {
      if (second.top() - 'a' <= ch[i]) {
        ans += second.top();
        second.pop();
      } else
        break;
    }
    second.push(s[i]);
  }
  while (!second.empty()) {
    ans += second.top();
    second.pop();
  }
  cout << ans;
}
