Area of triangle (function)

DECLARE FUNCTION AREA(A,B,C)
CLS
INPUT"ENTER FIRST NO";A
INPUT"ENTER SECOND NO";B
INPUT"ENTER THIRD NO";C
PRINT"AREA OF TRIANGLE";AREA(A,B,C)
END

FUNCTION AREA(A,B,C)
AREA=(S*(S-A)*(S-B*(S-C)^(1/2)
AREA=A
ENS FUNCTION