def find_missing_int_using_sum(complete, incomplete):
    """
    Problem: There are distinct integers in list `complete`. The same integers are in list `incomplete`, except for one.
    
    Task: Find the one integer which is missing from the incomplete list.

    Complexity: O(n) time, O(1) space
    """
    s = 0
    for a, b in zip(complete[:-1], incomplete):
        s += a
        s -= b
    return s + complete[len(complete) - 1]