#include<bits/stdc++.h>
using namespace std;

int main()
{
string S;cin>>S;string ans="yes";
set<char> Set;
for(int i=0;i<S.size();i++)
{
  if(!Set.count(S[i]))Set.insert(S[i]);
  else ans="no";
}
cout<<ans;
}
### Prompt

Please formulate 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;string ans="yes";
set<char> Set;
for(int i=0;i<S.size();i++)
{
  if(!Set.count(S[i]))Set.insert(S[i]);
  else ans="no";
}
cout<<ans;
}
```