A UPS tracking number, for domestic packages within the United States, will usually start with "1Z" followed by a 6 character shipper number (numbers and letters), a 2 digit service level indicator, and finally 8 digits identifying the package (the last digit being a check digit), for a total of 18 characters.\n\nWho has tracking numbers that start with 1z?
Please answer the following question by reasoning step-by-step.
A UPS
The relevant sentence in the passage is: A UPS tracking number, for domestic packages within the United States, will usually start with "1Z" followed by a 6 character shipper number (numbers and letters), a 2 digit service level indicator, and finally 8 digits identifying the package (the last digit being a check digit), for a total of 18 characters.

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Final answer: A UPS