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;
long long power(long long a, long long n) {
  long long p = 1;
  while (n > 0) {
    if (n % 2) {
      p = p * a;
    }
    n >>= 1;
    a *= a;
  }
  return p;
}
long long power(long long a, long long n, long long mod) {
  long long p = 1;
  while (n > 0) {
    if (n % 2) {
      p = p * a;
      p %= mod;
    }
    n >>= 1;
    a *= a;
    a %= mod;
  }
  return p % mod;
}
long long gcd(long long a, long long b) { return b ? gcd(b, a % b) : a; }
long long lcm(long long a, long long b) { return a * (b / gcd(a, b)); }
int main() {
  long long t = 1;
  while (t--) {
    string s;
    cin >> s;
    int n = s.length();
    multiset<char> ms;
    string u;
    stack<int> t;
    for (long long i = 0; i < s.length(); i++) ms.insert(s[i]);
    for (int i = 0; i < n; i++) {
      ms.erase(ms.find(s[i]));
      t.push(s[i]);
      while (t.empty() == false && ms.lower_bound(t.top()) == ms.begin()) {
        u += t.top();
        t.pop();
      }
    }
    cout << u;
  }
  return 0;
}
