Program fractii;
var n,i,j,cont : longint;
    m: qword;
    a: array[1..1000000] of byte;
    f1,f2: text;

Begin
     assign(f1,'fractii.in');
     reset(f1);
     readln(f1,n);
     close(f1);
     for i:=1 to n do
         a[i]:=0;
     cont:=0;
           m:=n*n-n+1;
           for i:=2 to trunc(sqrt(n)) do
               if a[i]=0 then
                for j:=i+1 to n do
                    if j mod i = 0 then a[j]:=1;
           for i:=1 to n do
               if a[i]=1 then inc(cont);
           m:=m-2*cont;
     assign(f2, 'fractii.out');
     rewrite(f2);
     writeln(f2,m);
     close(f2);
end.