{programmer:mogtaba amirzade 
url http:\\www.ifjam.com
}
program p13(input,output); {16:repeat form}
var
s:real;
k,j,n:integer;
begin
s:=1.0;
k:=0;
j:=1;
readln(n);
repeat
s:=s+k/j;
if k=0 then
k:=k-1;
k:=-k;
j:=j+1;
until j>n; {while}
writeln(s:1);
readln
end.