program fractii;
var i,j,n,s,a:longint;
    g,f:text;
function cmmdc(i,j:longint):longint;
var x,y:longint;
begin
x:=i;
y:=j;
while x<>y do
if x>y then
x:=x-y
else
y:=y-x;
cmmdc:=x;
end;
begin
assign(f,'fractii.in');
assign(g,'fractii.out');
reset(f);
rewrite(g);
readln(f,n);
for i:=1 to n div 2 do
for j:=1 to n do
if cmmdc(i,j)=1 then
s:=s+1;
s:=s*2-1;
if n mod 2=1 then
for j:=1 to n do
begin
i:=n div 2+1;
if cmmdc(i,j)=1 then
s:=s+1;
end;
writeln(g,s);
close(f);
close(g);
end.