Problem:
Score : 100 points

Problem Statement

In K-city, there are n streets running east-west, and m streets running north-south. Each street running east-west and each street running north-south cross each other. We will call the smallest area that is surrounded by four streets a block. How many blocks there are in K-city?

Constraints

2 ≤ n, m ≤ 100

Input

Input is given from Standard Input in the following format:

n m

Output

Print the number of blocks in K-city.

Sample Input 1

3 4

Sample Output 1

6

There are six blocks, as shown below:

Sample Input 2

2 2

Sample Output 2

1

There are one block, as shown below:

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

n = gets.chomp.to_i
a = gets.chomp.split(' ').map(&:to_i)
odd = a.select { |item| item % 2 != 0 }.count
even = n - odd
four = a.select { |item| item % 4 == 0}.count

if even - four > 0
  print odd > four ? 'No' : 'Yes'
else
  print odd > (four + 1) ? 'No' : 'Yes'
end