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 double EPS = 1e-6;
const int infi = (int)1e9;
const long long infl = (long long)1e16;
const int MOD = (int)1e9 + 7;
const int MAX = (int)2e5 + 10;
const int dx[] = {1, -1, 0, 0, 1, 1, -1, -1};
const int dy[] = {0, 0, -1, 1, 1, -1, 1, -1};
const int kdx[] = {1, 1, -1, -1, 2, 2, -2, -2};
const int kdy[] = {2, -2, 2, -2, 1, -1, 1, -1};
string s;
stack<char> st;
vector<char> t, u;
long long a[MAX];
int main() {
  cin >> s;
  long long n = s.size();
  a[n - 1] = (long long)s[n - 1];
  for (int i = n - 2; i >= 0; i--) {
    a[i] = min(a[i + 1], (long long)s[i]);
  }
  for (int i = 0; i < n; i++) {
    while (!st.empty() && (long long)st.top() <= a[i]) {
      u.push_back(st.top());
      st.pop();
    }
    if ((long long)s[i] == a[i])
      u.push_back(s[i]);
    else
      st.push(s[i]);
  }
  while (!st.empty()) {
    u.push_back(st.top());
    st.pop();
  }
  for (auto c : u) cout << c;
}
