var v:array[1..1000] of longint;
    u:array[0..50000] of longint;
    monede:array[1..1000] of longint;
    i, n, j:longint;
    l:longint;
    aux:longint;
    max:longint;
    f:text;

begin
assign (f,'economie.in'); reset (f);
readln (f, n);
max:=0;
for i := 1 to n do
  begin
  readln (f, v[i]);
  if v[i] > max then max:=v[i];
  end;
close (f);

for i := 1 to n-1 do
  for j := i+1 to n do
    if v[i] > v[j] then begin aux:=v[i]; v[i] := v[j]; v[j]:=aux; end;

l:=0;
for i := 1 to n do
  begin
  if u[i] = 0 then
    begin
    for j := 0 to max do
      begin
      if u[v[i] + j] = 0 then u[v[i]+j] := v[i];
      end;
    l:=l+1;
    monede[l] := v[i];
    end;
  end;

assign (f, 'economie.out'); rewrite (f);
writeln (f, l);
for i := 1 to l do writeln (f, monede[i]);
close (f);
end.