var
  a, b, y: real;
  s, l, i, j, n: integer;

begin
  write('введите n = ');
  readln(n);
  for i := 1 to n do 
  begin
    a := i / (i + 1) + a;
    s := 1;
    l := 1;
    for j := 1 to i do
    begin
      s := s * 2;
      l := l * 5;
    end;
    b := s / l + b;
  end;
  
  write('y = ', a / b:0:3);
end.