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;
stack<char> s;
string c;
int d[26], m, ans = 1;
pair<char, int> a[100000];
pair<int, char> b[100000];
int main() {
  cin >> c;
  for (int i = 0; i < c.size(); ++i) {
    a[i] = {c[i], i};
  }
  sort(a, a + c.size());
  b[0] = {a[0].second, a[0].first};
  char t = a[0].first;
  for (int i = 1; i < c.size(); ++i) {
    if (a[i].first != t) {
      t = a[i].first;
      d[m++] = ans;
      ++ans;
    } else {
      ++ans;
    }
    b[i] = {a[i].second, a[i].first};
  }
  d[m] = ans;
  sort(b, b + d[0]);
  for (int i = 1; i <= m; ++i) {
    sort(b + d[i - 1], b + d[i]);
  }
  m = 0;
  for (int i = 0; i < c.size(); ++i) {
    while (m <= b[i].first && i < c.size()) {
      s.push(c[m++]);
    }
    while (!s.empty()) {
      if (b[i].second >= s.top()) {
        cout << s.top();
        s.pop();
      } else {
        break;
      }
    }
  }
  while (!s.empty()) {
    cout << s.top();
    s.pop();
  }
  return 0;
}
