// x_tmp = A[16][16] * x[16] + A[16][17] * x[17]
		if(x[16] < 0) p = -x[16]; else p = x[16];
		tmp = p >> 1;
		sum = tmp;
		tmp >>= 3;
		sum += tmp;
		if(x[16] < 0){
			x_tmp =- sum;
		}else{
			x_tmp =  sum;
		}
		if(x[17] < 0) p = -x[17]; else p = x[17];
		tmp = p >> 1;
		sum = tmp;
		tmp >>= 1;
		sum += tmp;
		tmp >>= 1;
		sum += tmp;
		tmp >>= 1;
		sum += tmp;
		tmp >>= 1;
		sum += tmp;
		tmp >>= 1;
		sum += tmp;
		if(x[17] < 0){
			x_tmp += sum;
		}else{
			x_tmp -= sum;
		}
		x[17] = x[16];
		x[16] = x_tmp + y;

		// x_tmp = A[18][18] * x[18] + A[18][19] * x[19]
		if(x[18] < 0) p = -x[18]; else p = x[18];
		tmp = p;
		sum = tmp;
		tmp >>= 1;
		sum += tmp;
		tmp >>= 1;
		sum += tmp;
		tmp >>= 1;
		sum += tmp;
		tmp >>= 3;
		sum += tmp;
		tmp >>= 1;
		sum += tmp;
		tmp >>= 1;
		sum += tmp;
		tmp >>= 1;
		sum += tmp;
		tmp >>= 1;
		sum += tmp;
		if(x[18] < 0){
			x_tmp =  sum;
		}else{
			x_tmp =- sum;
		}
		if(x[19] < 0) p = -x[19]; else p = x[19];
		tmp = p >> 1;
		sum = tmp;
		tmp >>= 1;
		sum += tmp;
		tmp >>= 1;
		sum += tmp;
		tmp >>= 1;
		sum += tmp;
		tmp >>= 1;
		sum += tmp;
		tmp >>= 1;
		sum += tmp;
		tmp >>= 3;
		sum += tmp;
		if(x[19] < 0){
			x_tmp += sum;
		}else{
			x_tmp -= sum;
		}
		x[19] = x[18];
		x[18] = x_tmp + y;