var p:array[1..1000000] of longint;
    n,i:longint;
    f,g:text;

function euler(n:longint):int64;
var i,j:longint;
    nr:int64;
begin
nr:=1;
for i:=2 to n do
begin
     J:=2*i;
     while j<=n do
     begin
     p[j]:=p[j]-p[i];
     j:=j+i;
     end;
end;
for i:=2 to n do
nr:=nr+p[i]*2;
euler:=nr;
end;
begin
assign(f,'fractii.in');
assign(g,'fractii.out');
reset(f);
rewrite(g);
readln(f,n);
for I:=2 to n do
begin
     p[i]:=i-1;
end;
writeln(g,euler(n));
close(f);
close(g);
end.