1/ 

uses crt;
var A:array[1..1000] of integer;
    i,n,tong:integer;
begin
   clrscr;
   write('Nhap n: '); readln(n);
   for i:=1 to n do
   begin
      write('Nhap phan tu thu ',i,': ');
      readln(A[i]);
      if A[i] mod 2 = 0 then tong:=tong+A[i];
   end;
   writeln;
   write('Tong cac so chan la: ',tong);
   readln
end.

2/ 

uses crt;
var A:array[1..1000] of integer;
    i,n:integer; tich:longint;
begin
   clrscr;
   write('Nhap n: '); readln(n);
   tich:=1;
   for i:=1 to n do
   begin
      write('Nhap phan tu thu ',i,': ');
      readln(A[i]);
      tich:=tich*A[i];
   end;
   writeln;
   write('Tich la: ',tich);
   readln
end.

3/

uses crt;
var A:array[1..1000] of integer;
    i,n,tong:integer;
begin
   clrscr;
   write('Nhap n: '); readln(n);
   for i:=1 to n do
   begin
      write('Nhap phan tu thu ',i,': ');
      readln(A[i]);
      if A[i] mod 2 = 1 then tong:=tong+A[i];
   end;
   writeln;
   write('Tong cac so le la: ',tong);
   readln
end.