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 = 100000 + 10;
const int M = 1000000007;
const double PI = atan(1) * 4;
const int oo = 1000000000;
char s[N];
int nxt[N][26], ls[26];
stack<char> st;
int main() {
  scanf("%s", s);
  int n = strlen(s);
  memset(ls, -1, sizeof(ls));
  for (int i = n - 1; i >= 0; --i) {
    ls[s[i] - 'a'] = i;
    for (int j = 0; j < 26; ++j) nxt[i][j] = ls[j];
  }
  int cur = 0;
  string ans;
  while (cur < n) {
    for (int i = 0; i < 26; ++i)
      if (nxt[cur][i] != -1) {
        while (!st.empty() && st.top() - 'a' <= i) {
          ans += st.top();
          st.pop();
        }
        int d = nxt[cur][i];
        while (cur <= d) st.push(s[cur++]);
        while (!st.empty() && st.top() == i + 'a') {
          ans += st.top();
          st.pop();
        }
        break;
      }
  }
  while (!st.empty()) {
    ans += st.top();
    st.pop();
  }
  cout << ans << endl;
}
