Program fractii;
var n,i,j,cont : longint;
    m: longint;
    a: array[1..1000] of byte;
    fi,fo: text;

Begin
     assign(fi,'fractii.in');
     reset(fi);
     readln(fi,n);
     close(fi);
           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(fo, 'fractii.out');
     rewrite(fo);
     writeln(fo,m);
     close(fo);
end.