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 double PI = acos(-1.0);
const long long INFLL = 0x3f3f3f3f3f3f3f3fll;
const int maxn = 1e5 + 5;
const int mod = 1e9 + 7;
char s[maxn];
int a[maxn];
char ans[maxn];
bool have(char x) {
  for (int i = 0; i < x - 'a'; i++)
    if (a[i]) return 1;
  return 0;
}
int main() {
  while (~scanf("%s", s)) {
    stack<char> st;
    memset(a, 0, sizeof(a));
    int n = strlen(s);
    for (int i = 0; i < n; i++) {
      a[s[i] - 'a']++;
    }
    int cnt = 0;
    for (int i = 0; i < n; i++) {
      while (!st.empty() && !have(st.top())) {
        char tmp = st.top();
        st.pop();
        ans[cnt++] = tmp;
      }
      st.push(s[i]);
      a[s[i] - 'a']--;
    }
    while (!st.empty()) {
      ans[cnt++] = st.top();
      st.pop();
    }
    ans[cnt] = '\0';
    printf("%s", ans);
  }
  return 0;
}
