Two times two#2381
To develop the mathematical abilities of students, the following exercise is proposed. You are given a list consisting of unique random positive integers. The length of the list is from to . Count how many numbers in the list are equal to twice another number from the same list. You should write a program that reviews the lists and outputs, for each, the correct answer. For example, given the list:
1 4 3 2 9 7 18 22
Your program must output 3, because 2 = 2 \times 1, 4 = 2 \times 2, and 18 = 2 \times 9.
The input consists of one or more lists of numbers. Each line contains a list of distinct positive integers (from to numbers). All numbers do not exceed . Each line ends with a zero, which is not considered part of the list. A line with a single number indicates the end of input data. Some lists may have no numbers that are double another.
For each input list, print on a separate line the number of integers that are double another number in the same list.
Example 1