var f,g:text;
i,n,k:longint;
a,x:array[0..16000]of integer;
begin
assign(f,'reguli.in');
assign(g,'reguli.out');
reset(f);
rewrite(g);
readln(f,n);
for i:=1 to n do readln(f,x[i-1]);
i:=1;
k:=1;
a[k]:=x[1]-x[0];
while i<n do begin
if i mod k=0 then begin
if a[k]<>x[i]-x[i-1] then begin inc(k);
                                a[k]:=x[i]-x[i-1];
                          end;
end
else begin
  if x[i]-x[i-1]<>a[i mod k] then begin inc(k);
                                        a[k]:=x[i]-x[i-1];
                                  end;
  end;
inc(i);
end;
writeln(g,k);
for i:=1 to k do writeln(g,a[i]);
close(f);
close(g);
end.