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 N = 1e6 + 5;
const int inf = 1e8;
const int mod = 1e9 + 7;
int num[30];
char str[N];
char sum[N];
char u[N];
int main() {
  memset(num, 0, sizeof(num));
  scanf("%s", str);
  int len = strlen(str);
  int xb = 0;
  int st = 0;
  for (int i = (0); i < (len); ++i) {
    int x = str[i] - 'a';
    num[x]++;
  }
  int j = 0;
  for (int i = (0); i < (26); ++i) {
    char c = (char)i + 'a';
    while (st > 0 && sum[st] <= c) {
      u[xb++] = sum[st--];
    }
    while (num[i] > 0) {
      if (str[j] == c) {
        u[xb++] = str[j];
        num[i]--;
      } else {
        int x = str[j] - 'a';
        sum[++st] = str[j];
        num[x]--;
      }
      j++;
      if (j == len) break;
    }
    if (j == len) break;
  }
  for (int i = st; i > 0; i--) {
    u[xb++] = sum[i];
  }
  u[xb] = '\0';
  printf("%s", u);
  return 0;
}
