Problem:
Score : 100 points

Problem Statement

Snuke has N integers: 1,2,\ldots,N.
He will choose K of them and give those to Takahashi.

How many ways are there to choose K consecutive integers?

Constraints

All values in input are integers.

1 \leq K \leq N \leq 50

Input

Input is given from Standard Input in the following format:

N K

Output

Print the answer.

Sample Input 1

3 2

Sample Output 1

2

There are two ways to choose two consecutive integers: (1,2) and (2,3).

Sample Input 2

13 3

Sample Output 2

11

Solution in Ruby (2.3.3) (judge verdict: Time Limit Exceeded)

n, k = gets.strip.split.map(&:to_i)
a = n.times.map(&:to_i).combination(k)

def chk_seq(v)
  flag = true 
  s = v.sort
  a = s.shift
  s.each do |i|
    if a + 1 != i 
      flag = false
      break
    end
    a = i
  end
  flag
end

c = 0
a.each do |v|
  c += 1 if chk_seq(v)
end

puts c