Program fractii;
  uses crt;
  var i,n,s,p,j:integer;
  fi,fo:text;
begin
clrscr;
assign(fi,'fractii.in');
assign(fo,'fractii.out');
reset(fi);
rewrite(fo);
readln(fi,n);
p:=0;
for j:=1 to (n div 2) do begin
                          if (p<n) then
                          for i:=1 to n do  inc(s);
                          inc(p);
                          if (p<n) then
                          for i:=1 to n do if  (i=1) or ((i mod 2)<>0) then inc(s);
                          inc(p);
                          if (p<n) then
                          for i:=1 to n do if (i=1) or ((i mod 2)= 0) then inc(s);
                          inc(p);
                        end;



writeln(fo,s);
close(fo);
end.