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

int main()
{
    long long int a,b,c,x3=0,t;
    string s;set<char>k;
    cin>>s;
    for(int i=0;i<s.size();i++){
        k.insert(s[i]);}
    if(k.size()==s.size())cout<<"yes";
    else cout<<"no";
}
### Prompt

Develop a solution in CPP to the problem described below:

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()
{
    long long int a,b,c,x3=0,t;
    string s;set<char>k;
    cin>>s;
    for(int i=0;i<s.size();i++){
        k.insert(s[i]);}
    if(k.size()==s.size())cout<<"yes";
    else cout<<"no";
}
```