uses crt;
var n,i:integer;
s:real;
//chuongtrinhcon
function gthua(n:integer):real;
var gt:real;
i:integer;
begin
gt:=1;
for i:=1 to n do
gt:=gt*i;
gthua:=gt;
end;
//chuongtrinhcon
function lthua(n,x:integer):real;
var lt:real;
i:integer;
begin
lt:=1;
for i:=1 to x do lt:=lt*x;
lthua:=lt;
end;
//chuongtrinhchinh
begin
clrscr;
readln(n);
s:=0;
for i:=1 to n do
s:=s+(lthua(i,i)/gthua(i));
writeln(s:4:2);
readln;
end.