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 Go (1.6) (judge verdict: Accepted)

package main

import (
	"fmt"
	"os"
	"strings"
)

var (
	s string
)

func main() {
	fmt.Scan(&s)

	for i := 0; i < len(s); i++ {
		if strings.Contains(s[i+1:], string(s[i])) {
			fmt.Println("no")
			os.Exit(0)
		}
	}

	fmt.Println("yes")
}