var
s : real;
i,n : integer;
begin
s:=0;
readln(n);
for i := 15 to n do
s := s + 1/i;
write(s:5:2);
end.
var
s : real;
i,n : integer;
begin
s:=0;
readln(n);
for i := 15 to n do
s := s + 1/i;
write(s:5:2);
end.