program p1;
var x,a:array[4..500001] of int64;
    n,i,nr,r:0..500005;
    f:text;
    b:boolean;
begin
assign(f,'reguli.in');
reset(f);
readln(f,n);
for i:=0 to n-1 do
readln(f,x[i]);
close(f);
b:=false;
a[1]:=x[1]-x[0];
nr:=1;
for i:=2 to n-1 do
begin
a[i]:=x[i]-x[i-1];
if b=false then
if a[i]=a[1] then
begin
b:=true;
r:=i-1;
nr:=i-1;
end;
if b then
if a[i]<>a[i-r] then
begin
b:=false;
nr:=i;
end;
end;
assign(f,'reguli.out');
rewrite(f);
writeln(f,nr);
for i:=1 to nr do
writeln(f,a[i]);
close(f);
end.