typedef unsigned char u8;
typedef unsigned short u16;

struct u4
{
	u8 zero		: 4;
	u8 value	: 4;

	u4(){}
	u4(u8 _value) {
		zero = 0;
		value = _value;
	}
	const u4 operator+(const u4& b) { return value + b.value; }
	u4 operator+=(const u4& b) { return value + b.value; }
	bool operator==(const u4& b) { return value == b.value; }

	int check_overflow(u8 operand) const { return operand > (0xf - value) ? 1 : 0; }
};