area of box using function

DECLARE FUNCTION AREA(L,B,H)
CLS
INPUT"ENTER LENGTH";L
INPUT"ENTER BREADTH";B
INPUT"ENTER HEIGHT";H
PRINT"AREA OF A BOX";AREA(L,B,H)
END

FUNCTION AREA(L,B,H)
A=2*(L*H+B*H+L*B)
AREA=A
END FUNCTION