The set U can be rewritten by listing its elements as follows:
U = {..., -6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, ...}
In this notation, the "..." symbol indicates that the set continues in both the negative and positive direction, and that all integers from negative infinity to positive infinity are included in the set. This notation is commonly used to represent sets of integers or other infinite sets in mathematics.