Вычислить произведение только отрицательных из трех данных чисел

program Product;
 
var x, y, z, r: real;
    i: integer;
 
begin
  write('x = '); readln(x);
  write('y = '); readln(y);
  write('z = '); readln(z);
  r := 1;
  i := 0;
  if (x < 0) then begin r := r * x; i := i + 1; end;
  if (y < 0) then begin r := r * y; i := i + 1; end;
  if (z < 0) then begin r := r * z; i := i + 1; end;
  case i of
    0: writeln('No negative numbers');
    1: writeln('Only one negative number, no calculate product')
    else writeln('Product of negative numbers in x, y, z = ', r);
  end;
  readln;
end.

program Sum;
 
var x, y, z, w, r, i: integer;
 
begin
  write('x = '); readln(x);
  write('y = '); readln(y);
  write('z = '); readln(z);
  write('w = '); readln(w);
  r := 0;
  i := 0;
  if not(odd(x)) then begin r := r + x; i := i + 1; end;
  if not(odd(y)) then begin r := r + y; i := i + 1; end;
  if not(odd(z)) then begin r := r + z; i := i + 1; end;
  if not(odd(w)) then begin r := r + w; i := i + 1; end;
  if i = 0 then writeln('No even numbers')
           else writeln('Sum of even numbers in x, y, z, w = ', r);
  readln;
end.