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;
const int MAXN = 1e5 + 10;
const int INF = 0x3f3f3f3f;
char s[MAXN], minn[MAXN];
int main() {
  scanf("%s", s);
  int len = strlen(s);
  for (int i = len - 1; i >= 0; i--) {
    if (i == len - 1)
      minn[i] = s[i];
    else
      minn[i] = min(minn[i + 1], s[i]);
  }
  stack<char> st;
  char top;
  for (int i = 0; i < len; i++) {
    if (st.empty())
      st.push(s[i]);
    else {
      while (!st.empty()) {
        top = st.top();
        if (top <= minn[i]) {
          st.pop();
          printf("%c", top);
        } else
          break;
      }
      st.push(s[i]);
    }
  }
  while (!st.empty()) {
    top = st.top();
    printf("%c", top);
    st.pop();
  }
  return 0;
}
