To determine whether the piece begins with a downbeat or an upbeat, we can consider the context of the score where the time signature is in common time (4/4). In music, a downbeat occurs on the first beat of the measure, while an upbeat occurs on the last beat (or beats) leading into the next measure.
If the score starts directly with a note on the first beat of the first measure, it is considered a downbeat. If it starts with a rest or notes that lead into the first beat, creating a pickup to the first complete measure, it would be considered an upbeat.
Since the score begins with the symbol for common time but you did not provide details stating an initial rest or other information, we can reasonably conclude that it begins with a note directly on the first beat.
Therefore, the answer is:
downbeat