#include <bits/stdc++.h>

using namespace std;

int main() {
  string s; cin >> s;
  set <char> st(s.begin(), s.end());
  if(st.size() == s.length()) printf("yes");
  else printf("no");
}
### 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;
  set <char> st(s.begin(), s.end());
  if(st.size() == s.length()) printf("yes");
  else printf("no");
}
```