var a,b,n,ct,c:integer;
    f,g:text;

begin
assign(f,'fractii.in');
assign(g,'fractii.out');
reset(f);
read(f,n);
close(f);
a:=1;
b:=1;
c:=1;
while (a<=n) and (b<=n) do
  Begin
     while b<=n do
     begin
        if (a mod 2<>0) and (a<>b) then
        c:=c+1;
        if (a mod 2=0) then begin
           if (b mod 2<>0) then
           c:=c+1
        end;
      b:=b+1
     end;
  a:=a+1;
  b:=1;
end;
rewrite(g);
write(g,c);
close(g)
END.