var
a,b,c,d,e,l,m,n: integer ;
begin
read(a);
if (a = 2) then writeln('13') else
if (a = 1) then writeln('5') else
if (a = 3) then writeln((a*4) + 1 + (3*4)) else
begin
b:= (a*4) + 1;
n:= b + 4+(2*(a-1))*(2*(a-1)) ;
writeln(n);
end;
end.