#include <bits/stdc++.h>
using namespace std;
int main(){
  string S;
  cin>>S;
  sort(S.begin(),S.end());
  int i;
  for(i=1;i<S.size();i++)if(S.at(i)==S.at(i-1))break;
  if(i==S.size())cout<<"yes"<<endl;
  else cout<<"no"<<endl;
}
### Prompt

Your task is to create 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;
  sort(S.begin(),S.end());
  int i;
  for(i=1;i<S.size();i++)if(S.at(i)==S.at(i-1))break;
  if(i==S.size())cout<<"yes"<<endl;
  else cout<<"no"<<endl;
}
```