var a:array[1..1000000,1..7] of longint;
    b:array[1..1000000]of longint;
    n,r,x,i,j,k:longint;
    p:boolean;
    f,g:text;

begin
assign(f,'fractii.in');
reset(f);
assign(g,'fractii.out');
rewrite(g);
readln(f,n);
for i:=2 to n div 2 do begin
   if b[i]=0 then begin
                  x:=i*2;
                  while x<n+1 do begin
                    b[x]:=b[x]+1;
                    a[x,b[x]]:=i;
                    x:=x+i;
                  end;
                  end;
end;
r:=n;
for i:=2 to n do begin
   for j:=i+1 to n do begin
      p:=j mod i<>0;
      x:=j-i;
      for k:=1 to b[i] do p:=p and(x mod a[i,k]<>0);
      if p then r:=r+1;
   end;
end;
r:=r*2-1;
write(g,r);
close(g);
end.