CHARACTER(26) S,ABC
INTEGER X(26)
READ*,S
ABC="abcdefghijklmnopqrstuvwxyz"
X=0
DO I=1, LEN_TRIM(S)
  DO J=1,26
   IF ( S(I:I)==ABC(J:J) ) X(J)=X(J)+1
  END DO
END DO
PRINT"(A)",MERGE("yes"," no",MAXVAL(X)==1)
END 