var f,g:text;
    x,y,i,j,n,s:longint;

function divizor(x,y:integer):integer;
BEGIN
while x<>y do
if x>y then x:=x-y
       else y:=y-x;
divizor:=x;
end;

BEGIN
assign(f,'fractii.in');reset(f);
assign(g,'fractii.out');rewrite(g);
read(f,n);
close(f);
s:=2*n-1;
for i:=2 to n  do begin
if i mod 2=0 then s:=s+2;
if i mod 2=1 then s:=s+3;
end;
write(g,s);

close(g);
end.