program abc;
var s:real;
i,n:integer;
begin
readln(n);
repeat
for i:=1 to n do
S:=s+6/7/n
until i=n ;
writeln(s);
end.
program abc;
var s:real;
i,n:integer;
begin
readln(n);
repeat
for i:=1 to n do
S:=s+6/7/n
until i=n ;
writeln(s);
end.