#include <bits/stdc++.h>

using namespace std;

int main(){
  string s; cin >> s;
  set<char> uni;
  for(int i=0;i<s.size();++i) uni.insert(s[i]);
  cout << (uni.size()==s.size()?"yes":"no") << endl;
  
  return 0;
}

### Prompt

Create a solution in cpp for 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> uni;
  for(int i=0;i<s.size();++i) uni.insert(s[i]);
  cout << (uni.size()==s.size()?"yes":"no") << endl;
  
  return 0;
}

```