uses crt;
var i,n:integer;
s:real;
//ham tinh giai thua
function gt(n:integer):longint;
var i,gthua:longint;
begin
gthua:=1;
for i:=1 to n do gthua:=gthua*i;
gt:=gthua;
end;
begin
clrscr;
readln(n);
s:=0;
for i:=1 to n do
s:=s+1/(gt(i));
writeln(s:4:2);
readln;
end.