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: Accepted)

#include <stdio.h>
#include <string.h>

void swap(int* a, int* b)
{
    int c = *a;
    *a = *b;
    *b = c;
}

int main()
{
    char s[30];
    scanf("%27s", s);
    int a[30];
    int i = 0;
    int cnt = 0;
    for (i = 0; i < 30; i++)
    {
        if (s[i] == '\0')
        {
            cnt = i;
            break;
        }
        a[i] = s[i];
    }
    int changed = 1;
    while (changed == 1)
    {
        changed = 0;
        for (i = 0; i < cnt - 1; i++)
        {
            if (a[i] > a[i + 1])
            {
                swap(&a[i], &a[i+1]);
                changed = 1;
            }
        }
    }
    int diffed = 1;
    for (i = 0; i < cnt - 1; i++)
    {
        if (i == 0)
        {
            if (a[i] == a[i + 1])
            {
                diffed = 0;
            }
        }
        else
        {
            if (a[i - 1] == a[i])
            {
                diffed = 0;
            }
            else if (a[i] == a[i + 1])
            {
                diffed = 0;
            }
        }
    }
    if (diffed)
    {
        printf("yes\n");
    }
    else
    {
        printf("no\n");
    }
    return 0;
}