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;
int main() {
  vector<char> st, alt, u;
  char curr;
  while (scanf("%c", &curr), curr != '\n') {
    st.push_back(curr);
  }
  alt.assign(st.size(), 'z');
  alt[alt.size() - 1] = st[st.size() - 1];
  for (int i = st.size() - 2; i >= 0; i--) {
    if (st[i] >= alt[i + 1])
      alt[i] = alt[i + 1];
    else
      alt[i] = st[i];
  }
  stack<char> t;
  int sti = 0;
  while (sti < st.size() || !t.empty()) {
    if (t.empty()) {
      t.push(st[sti]);
      sti++;
      continue;
    }
    if (sti >= st.size()) {
      u.push_back(t.top());
      t.pop();
      continue;
    }
    if (alt[sti] >= t.top()) {
      u.push_back(t.top());
      t.pop();
      continue;
    }
    if (alt[sti] < t.top()) {
      t.push(st[sti]);
      sti++;
      continue;
    }
  }
  for (int i = 0; i < u.size(); i++) printf("%c", u[i]);
  printf("\n");
  return 0;
}
