#include<bits/stdc++.h>
using namespace std;
int main(){
  string s;
  cin >> s;
  int i,n=s.size();
  string t="yes";
  for(i=0;i<n;i++){
    for(int j=i+1;j<n;j++){
      if(s.at(i)==s.at(j)){
        t="no";
      }
    }
  }
  cout << t;
}
### Prompt

Generate a Cpp solution to the following problem:

You are given a string S consisting of lowercase English letters. Determine whether all the characters in S are different.

Constraints

* 2 ≤ |S| ≤ 26, where |S| denotes the length of S.
* S consists of lowercase English letters.

Input

Input is given from Standard Input in the following format:


S


Output

If all the characters in S are different, print `yes` (case-sensitive); otherwise, print `no`.

Examples

Input

uncopyrightable


Output

yes


Input

different


Output

no


Input

no


Output

yes

### Response

```cpp
#include<bits/stdc++.h>
using namespace std;
int main(){
  string s;
  cin >> s;
  int i,n=s.size();
  string t="yes";
  for(i=0;i<n;i++){
    for(int j=i+1;j<n;j++){
      if(s.at(i)==s.at(j)){
        t="no";
      }
    }
  }
  cout << t;
}
```