var a:array[1..1000000]of integer;
    b:array[1..80000]of longint;
    n,i,j,z,x:longint;
    s:int64;
begin
     assign(input,'fractii.in');
     reset(input);
     assign(output,'fractii.out');
     rewrite(output);
     readln(n);
     for i:=2 to n do
     begin
          if a[i]=0 then
          begin
               z:=z+1;
               b[z]:=i;
          end;
          j:=i;
          if a[i]=0 then
          while j<=n do
          begin
               j:=j+i;
               if j>n then break;
               a[j]:=1;
          end;
     end;
     if n=2 then s:=2;
     for i:=1 to z do
     begin
          if b[i]<=n div 2 then s:=s+n div b[i]-1;
          x:=n-n div b[i];
          s:=s+x;
          s:=s+(x-z+1);
     end;
     s:=s+(n-z)*2-1;
     s:=s-1;
     writeln(s);
close(output);
end.