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;
char s[maxn];
vector<char> ans;
stack<char> stk;
int cnt[30], len;
int main() {
  gets(s);
  len = strlen(s);
  for (int i = 0; i < len; i++) {
    cnt[s[i] - 'a']++;
  }
  int pos = 0;
  while (pos < len) {
    int temp = 0;
    for (int i = 0; i < 26; i++)
      if (cnt[i] > 0) {
        temp = i;
        break;
      }
    if (!stk.empty() && stk.top() <= (temp + 'a')) {
      ans.push_back(stk.top());
      stk.pop();
      continue;
    }
    while (pos < len) {
      if (s[pos] > (temp + 'a')) {
        stk.push(s[pos]);
        cnt[s[pos] - 'a']--;
        pos++;
      } else {
        ans.push_back(s[pos]);
        cnt[s[pos] - 'a']--;
        pos++;
        break;
      }
    }
  }
  while (!stk.empty()) {
    ans.push_back(stk.top());
    stk.pop();
  }
  for (int i = 0; i < ans.size(); i++) {
    printf("%c", ans[i]);
  }
  printf("\n");
  return 0;
}
