#include <bits/stdc++.h>
#define ll long long
using namespace std;
int main(void){
 string s; cin >> s;
 for(int i=0;i<s.size();i++)for(int j=0;j<i;j++){
  if (s[i]==s[j]) {cout << "no" << endl; return 0;} 
 }
 cout << "yes" << endl;
 return 0;
}

### 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>
#define ll long long
using namespace std;
int main(void){
 string s; cin >> s;
 for(int i=0;i<s.size();i++)for(int j=0;j<i;j++){
  if (s[i]==s[j]) {cout << "no" << endl; return 0;} 
 }
 cout << "yes" << endl;
 return 0;
}

```