Problem:
Score : 200 points

Problem Statement

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.

Sample Input 1

uncopyrightable

Sample Output 1

yes

Sample Input 2

different

Sample Output 2

no

Sample Input 3

no

Sample Output 3

yes

Solution in C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include<algorithm>
#include<cmath>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<functional>
#include<iomanip>
#include<iostream>
#include<list>
#include<map>
#include<queue>
#include<random>
#include<set>
#include<stack>
#include<string>
#include<utility>
#include<vector>

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define rep(i,n)   FOR(i,0,n)
#define FORR(i,a,b) for(int i=(a);i>=(b);--i)
#define REPR(i,n)   FORR(i,n,0)
#define int long long

using namespace std;
typedef pair<int, int> pii;

string s;
int a[30]={0};

signed main() {
	cin>>s;
    bool f=true;
	rep(i,s.length()){
        if(a[s[i]-97]!=0){
            f=false;
        }
        a[s[i]-97]++;
    }
	
    if(f){
        cout<<"yes"<<endl;
    }
    else{
        cout<<"no"<<endl;
    }

	return 0;
}