REM to ask full name from user and displays only last name:

CLS

INPUT "Enter your full name using commas instead of spaces:", a$, b$, c$

PRINT "Your last name is:", c$

END

or,

CLS
INPUT "Enter your full name:  ", N$
INPUT "Enter your caste digit:(eg. Rai=3): ", D
A = LEN(N$) - D
FOR I = 1 TO D
A = A + 1
C$ = C$ + MID$(N$, A, 1)
NEXT I
PRINT
PRINT "Your caste is:", UCASE$(C$)
END