Qbasic to find positive or negative using Sub

DECLARE SUB CHECK(N)
CLS
INPUT"ENTER ANY NO.";N
CALL CHECK (N$)
END


SUB CHECK(N)
IF N > 0 THEN
PRINT "POSITIVE NO."
ELSEIF N  < 0 THEN
PRINT "NEGATIVE NO."
ELSE
PRINT "ZERO"
END IF
END SUB