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;
char strf[100005], strt[100005];
int cnt[26];
stack<int> S;
int main() {
  scanf("%s", strf);
  memset(cnt, 0, sizeof(cnt));
  int len = strlen(strf);
  for (int i = 0; i < len; i++) cnt[strf[i] - 'a']++;
  int pnf = 0, pnt = 0;
  for (int i = 0; i < 26; i++) {
    if (pnt == len) break;
    if (cnt[i] == len) {
      printf("%s\n", strf);
      return 0;
    }
    while ((!S.empty()) && S.top() <= i + 'a') {
      strt[pnt++] = S.top();
      S.pop();
    }
    while (cnt[i] > 0) {
      if (strf[pnf] - 'a' == i) {
        strt[pnt++] = strf[pnf];
        pnf++;
        cnt[i]--;
        continue;
      } else {
        S.push(strf[pnf]);
        cnt[strf[pnf] - 'a']--;
        pnf++;
      }
    }
  }
  while (!S.empty()) {
    strt[pnt++] = S.top();
    S.pop();
  }
  for (int i = 0; i < len; i++) printf("%c", strt[i]);
  printf("\n");
  return 0;
}
