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 JavaScript (node.js v5.12) (judge verdict: Accepted)

/**
 * @param {String} input
 */
function Main(input){
	var letterMap = {};
	while( input ){
		var letter = input.charAt(0);
		if(letterMap[letter]){
			return "no";
		}
		letterMap[letter] = true;
		input = input.slice( 1 );
	}
    return "yes"; 
}
console.log(Main(require("fs").readFileSync("/dev/stdin", "utf8")));