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 long long int mod = 1e9 + 7;
long long int poww(long long int x, long long int n) {
  long long int res = 1;
  while (n > 0) {
    if (n % 2) res *= x;
    n = n >> 1;
    x *= x;
  }
  return res;
}
void solve() {
  string s;
  cin >> s;
  vector<long long int> freq(26, 0);
  for (char c : s) freq[c - 'a']++;
  stack<char> st;
  long long int ptr = 0;
  string ans = "";
  long long int n = s.size();
  for (int i = 0; i < n; i++) {
    while (ptr < 25 and freq[ptr] == 0) ptr++;
    if (st.empty())
      st.push(s[i]), freq[s[i] - 'a']--;
    else {
      while (!st.empty() and st.top() <= 'a' + ptr) {
        ans += st.top();
        st.pop();
      }
      st.push(s[i]);
      freq[s[i] - 'a']--;
      if (freq[ptr] == 0) ptr++;
    }
  }
  while (!st.empty()) ans += st.top(), st.pop();
  cout << ans << endl;
}
int main() {
  ios::sync_with_stdio(0), cout.tie(0), cin.tie(0);
  ;
  { solve(); }
}
