Problem:
Score : 100 points

Problem Statement

How many multiples of d are there among the integers between L and R (inclusive)?

Constraints

All values in input are integers.

1 \leq L \leq R \leq 100

1 \leq d \leq 100

Input

Input is given from Standard Input in the following format:

L R d

Output

Print the number of multiples of d among the integers between L and R (inclusive).

Sample Input 1

5 10 2

Sample Output 1

3

Among the integers between 5 and 10, there are three multiples of 2: 6, 8, and 10.

Sample Input 2

6 20 7

Sample Output 2

2

Among the integers between 6 and 20, there are two multiples of 7: 7 and 14.

Sample Input 3

1 100 1

Sample Output 3

100

Solution in Ruby (2.7.1) (judge verdict: Wrong Answer)

n = gets.to_i
c = 0
for i in 1..n
  c = 0
  max = i/3
  for t in 1..max
    x = t
    if c != 0
      break
    end
    for q in 1..i/3+3-t
      y = q
      if c != 0
        break
      end
      for r in 1..i/3+3-(t+q)
        z = r
        ch = x*x + y*y + z*z + x*y + y*z + z*x
        if i == ch
          if x == y && y == z
            c = 1
            break
          elsif x == y || y == z || z == x
            c += 3
            break
          else
            c += 9
            break
          end
        elsif i < ch
          break
        end
      end
    end
  end
  puts c
end