#include <bits/stdc++.h>
using namespace std;
string s; set<char> d;
int main() {
	cin >> s;
	for(char c : s) d.insert(c);
	cout << (s.size() == d.size() ? "yes" : "no") << endl;
	return 0;
}
### 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;
string s; set<char> d;
int main() {
	cin >> s;
	for(char c : s) d.insert(c);
	cout << (s.size() == d.size() ? "yes" : "no") << endl;
	return 0;
}
```