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>
const int MAX = 200010;
const long long MOD = 1e9 + 7;
const int INF = 0x3f3f3f3f;
const long long LLINF = 0x3f3f3f3f3f3f3f3f;
const long double EPS = 1e-6;
const long double PI = acos(-1.0);
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  string s;
  cin >> s;
  vector<char> fila, ans;
  vector<int> num(30, 0);
  for (auto c : s) num[c - 'a']++;
  for (auto c : s) {
    fila.push_back(c);
    num[c - 'a']--;
    bool t = false;
    while (!t and !fila.empty()) {
      for (int i = 0; i < fila.back() - 'a'; i++)
        if (num[i] > 0) t = true;
      if (!t) {
        ans.push_back(fila.back());
        fila.pop_back();
      }
    }
  }
  while (!fila.empty()) {
    ans.push_back(fila.back());
    fila.pop_back();
  }
  for (auto c : ans) cout << c;
  cout << '\n';
  return 0;
}
