sum of two number in pl/sql

CREATE OR REPLACE PROCEDURE TOTAL
( N1 IN NUMBER,N2 IN NUMBER,S OUT NUMBER)
IS
BEGIN
S:= N1+N2;
END;

DECLARE
A NUMBER(5);
B NUMBER(5);
S NUMBER(7);
BEGIN
A:= :ENTER_NUMBER_A;
B:= :ENTER_NUMBER_B;
TOTAL(A,B,S);
DBMS_OUTPUT.PUT_LINE('SUM IS' || S);
END;