typedef uint32_t binary;
typedef uint64_t ternary;

ternary seed() { return (ternary)0; }

ternary terplus(ternary sum, binary x)
{
  // удобно выбрать коды 00, 01, 11

  // hl   x
  // 00 + 0 = 00
  // 00 + 1 = 01
  // 01 + 0 = 01
  // 01 + 1 = 11
  // 11 + 0 = 11
  // 11 + 1 = 00

  binary h = (binary)(sum >> 32);
  binary l = (binary)(sum);

  binary L = ~(h&l&x) & (h|l|x);
  binary H = l&(h^x);

  return ((ternary)H << 32) | L;
}

binary answer(ternary sum)
{
  binary h = (binary)(sum >> 32);
  binary l = (binary)(sum);

  assert(h == 0);
  return l;
}

template<class SERIES>
binary find_unique(SERIES series)
{
  ternary sum = seed();
  int num = 0;
  for(binary x : series)
  {
    sum = terplus(sum,x);
    num++;
  }
  assert(num % 3 == 1);
  return answer(sum);
}