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 U;
stack<char> T;
vector<int> letter[26];
void solve(int x, int sta) {
  int i, k;
  while (!T.empty() && T.top() <= x + 'a') {
    printf("%c", T.top());
    T.pop();
  }
  if (x == 25) {
    k = lower_bound(letter[x].begin(), letter[x].end(), sta) -
        letter[x].begin();
    if (k == letter[x].end() - letter[x].begin()) {
      while (!T.empty()) {
        printf("%c", T.top());
        T.pop();
      }
      return;
    }
    for (i = sta; i <= letter[x][letter[x].size() - 1]; i++) {
      if (i < letter[x][k])
        T.push(U[i]);
      else {
        printf("%c", U[i]);
        k++;
      }
    }
    while (!T.empty()) {
      printf("%c", T.top());
      T.pop();
    }
    return;
  }
  k = lower_bound(letter[x].begin(), letter[x].end(), sta) - letter[x].begin();
  if (k == letter[x].end() - letter[x].begin()) {
    solve(x + 1, sta);
    return;
  }
  for (i = sta; i <= letter[x][letter[x].size() - 1]; i++) {
    if (i < letter[x][k])
      T.push(U[i]);
    else {
      printf("%c", U[i]);
      k++;
    }
  }
  solve(x + 1, i);
}
int main() {
  int i;
  cin >> U;
  for (i = 0; i < U.length(); i++) letter[U[i] - 'a'].push_back(i);
  solve(0, 0);
  return 0;
}
