var  n,nr,i,j:1..1000000;   f:text;
begin
Assign(f,'fractii.in');
reset(f);
Readln(f,n);
nr:=n;
For i:=2 to n do
 begin
  if odd(i)=false then  begin
                         For j:=1 to n do
                          if odd(j)=true then nr:=nr+1;
                        end
                  else  begin
                         For j:=2 to n do
                          if odd(j)=false then nr:=nr+1;
                         nr:=nr+1;
                        end;
 end;
 Assign(f,'fractii.out');
 rewrite(f);
Writeln(f,nr);
close(f);
end.