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 MAXN = (int)5e5 + 228;
const char nxtl = '\n';
const int mod = (int)1e9 + 7;
const double eps = (double)1e-7;
template <typename T>
inline bool updmin(T &a, const T &b) {
  return a > b ? a = b, 1 : 0;
}
template <typename T>
inline bool updmax(T &a, const T &b) {
  return a < b ? a = b, 1 : 0;
}
char suf[MAXN];
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  string s;
  cin >> s;
  suf[((int)(s.size())) - 1] = s.back();
  suf[((int)(s.size()))] = 'z' + 1;
  for (int i = ((int)(s.size())) - 2; i >= 0; --i)
    suf[i] = min(suf[i + 1], s[i]);
  vector<char> v;
  string res = "";
  for (int i = 0; i <= ((int)(s.size())) - 1; ++i) {
    v.push_back(s[i]);
    while (!v.empty() && v.back() <= suf[i + 1]) {
      res += v.back();
      v.pop_back();
    }
  }
  while (!v.empty()) {
    res += v.back();
    v.pop_back();
  }
  cout << res << nxtl;
  return 0;
}
