var k, l, m, N: integer;
s: longint = 0;
begin
k := 0;
write('N: ');
readln(N);
for l := 1 to N do
begin
readln(m);
if (m mod 7 = 4) then
begin
inc(k);
s := s + m
end
end;
if (k > 0) then writeln(s / k)
else writeln('NO')
end.