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;
string s;
vector<vector<int>> v(26);
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cin >> s;
  int n = s.size();
  for (int i = 0; i < n; i++) {
    int c = s[i] - 'a';
    v[c].emplace_back(i);
  }
  vector<int> u;
  for (int i = 0; i < 26; i++) {
    for (int x : v[i]) {
      u.emplace_back(x);
    }
  }
  string res = "";
  stack<int> st;
  int i = 0, j = 0;
  while (j < n) {
    while (j < n && u[j] < i) {
      j++;
    }
    if (j >= n) break;
    while (!st.empty() && s[st.top()] <= s[u[j]]) {
      res.push_back(s[st.top()]);
      st.pop();
    }
    while (i < u[j]) {
      st.push(i);
      i++;
    }
    res.push_back(s[i++]);
    j++;
  }
  while (!st.empty()) {
    res.push_back(s[st.top()]);
    st.pop();
  }
  cout << res << '\n';
}
