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 = 1e5 + 10;
const double eps = 1e-9;
const int inf = 1e9;
char a[N];
int frq[30];
set<char> st;
string ans;
queue<char> q;
vector<char> v;
int main() {
  scanf("%s", a);
  int n = strlen(a);
  for (int i = 0; i < n; i++) {
    frq[a[i] - 'a']++;
    st.insert(a[i]);
    q.push(a[i]);
  }
  for (auto x : st) {
    while (v.size() && v.back() <= x) {
      ans.push_back(v.back());
      v.pop_back();
    }
    while (q.size() && frq[x - 'a']) {
      char xx = q.front();
      q.pop();
      frq[xx - 'a']--;
      if (xx == x)
        ans.push_back(xx);
      else
        v.push_back(xx);
    }
  }
  reverse(v.begin(), v.end());
  for (auto x : v) ans += x;
  printf("%s", ans.c_str());
}
