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 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<stdio.h>
int main(void){
	int i,a,k;
	char S[256];
	scanf("%s", S);
	for (i = 0; i < 26; i++){
		for (a = 0; a < 26; a++){
			if (S[i] == S[a]){
				k = 1;
			}
		}
	}
	if (k = 1){
		printf("no");
	}
	else{
		printf("yes");
	}
}