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;
inline int read() {
  int x = 0, f = 1;
  char ch = getchar();
  while (ch < '0' || ch > '9') {
    if (ch == '-') f = -1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9') {
    x = x * 10 + ch - '0';
    ch = getchar();
  }
  return x * f;
}
char a[100005];
char m[100005];
stack<char> Q;
string str;
int n;
int main(void) {
  gets(a);
  n = strlen(a);
  m[n - 1] = a[n - 1];
  for (int i = n - 2; i >= 0; --i) m[i] = min(m[i + 1], a[i]);
  for (int i = 0; i < n; ++i) {
    while (!Q.empty() && Q.top() <= m[i]) {
      str.push_back(Q.top());
      Q.pop();
    }
    Q.push(a[i]);
  }
  while (!Q.empty()) {
    str.push_back(Q.top());
    Q.pop();
  }
  puts(str.c_str());
  return 0;
}
