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 Fortran (GNU Fortran 9.2.1) (judge verdict: Accepted)

program prob2
    implicit none
    character(len=30)::s
    integer::c(26), i, l, tmp
    c = 0
    read(*,*) s
    l = len_trim(s)
    do i = 1, l
        tmp = ichar(s(i:i)) - ichar('a') + 1
        if(c(tmp) == 1) then
            write(*,'(a)') "no"
            stop
        else
        	c(tmp) = 1
        end if
    end do
    write(*,'(a)') "yes"
    stop
end program