Problem:
Score : 100 points

Problem Statement

It has been decided that a programming contest sponsored by company A will be held, so we will post the notice on a bulletin board.

The bulletin board is in the form of a grid with N rows and N columns, and the notice will occupy a rectangular region with H rows and W columns.

How many ways are there to choose where to put the notice so that it completely covers exactly HW squares?

Constraints

1 \leq H, W \leq N \leq 100

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N
H
W

Output

Print the answer.

Sample Input 1

3
2
3

Sample Output 1

2

There are two ways to put the notice, as follows:

### ...
### ###
... ###

Here, # represents a square covered by the notice, and . represents a square not covered.

Sample Input 2

100
1
1

Sample Output 2

10000

Sample Input 3

5
4
2

Sample Output 3

8

Solution in Ruby (2.3.3) (judge verdict: Accepted)

n = gets.chomp.to_i
h = gets.chomp.to_i
w = gets.chomp.to_i

count = 0
1.upto n do |height|
  if h+height-1 <= n
    1.upto n do |width|
      if w+width-1 <= n
        count += 1
      else
        next
      end
    end
  else
    next
  end
end

puts count