#include <bits/stdc++.h>
using namespace std;
int a[30]={};
int main(){
	string s;
	cin>>s;
	int d=s.size();
	for(int i=0;i<d;i++){
		a[s[i]-97]++;
	}
	for(int i=0;i<26;i++){
	if(a[i]>1){cout<<"no"<<endl;return 0;}
	}
	cout<<"yes"<<endl;
}

### Prompt

In cpp, your task is to solve 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 a[30]={};
int main(){
	string s;
	cin>>s;
	int d=s.size();
	for(int i=0;i<d;i++){
		a[s[i]-97]++;
	}
	for(int i=0;i<26;i++){
	if(a[i]>1){cout<<"no"<<endl;return 0;}
	}
	cout<<"yes"<<endl;
}

```