Problem:
Score : 100 points

Problem Statement

You are given positive integers A and B.

If A is a divisor of B, print A + B; otherwise, print B - A.

Constraints

All values in input are integers.

1 \leq A \leq B \leq 20

Input

Input is given from Standard Input in the following format:

A B

Output

If A is a divisor of B, print A + B; otherwise, print B - A.

Sample Input 1

4 12

Sample Output 1

16

As 4 is a divisor of 12, 4 + 12 = 16 should be printed.

Sample Input 2

8 20

Sample Output 2

12

Sample Input 3

1 1

Sample Output 3

2

1 is a divisor of 1.

Solution in Ruby (2.3.3) (judge verdict: Runtime Error)

n, m = gets.chomp.split.map(&:to_i)
a = Array.new(n) { Array.new }
n.times do |i|
  a[i] = gets.chomp.split.map(&:to_i)
end

d = a[0].slice(1..a[0].size)
n.times do |i|
  if i == 0
    next
  end

  if a[0].size < 20
    1 / 0
  end

  a[i].slice!(1..a[i].size)
  d.each do |j|
    unless a[i].include?(j)
      d.delete(j)
    end
  end
end

p d.size