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 (gfortran v4.8.4) (judge verdict: Accepted)

program main
  implicit none
  character(26) :: s
  integer :: i, j, n
  read(*, *) s
  n = len(trim(s))
  do i = 1, n
    do j = i + 1, n
      if (s(i:i) == s(j:j)) then
        write(*, "(a)") "no"
        stop 0
      end if
    end do
  end do
  write(*, "(a)") "yes"
end program main