Problem:
Score : 300 points

Problem Statement

You are given two non-negative integers L and R.
We will choose two integers i and j such that L \leq i < j \leq R.
Find the minimum possible value of (i \times j) \mbox{ mod } 2019.

Constraints

All values in input are integers.

0 \leq L < R \leq 2 \times 10^9

Input

Input is given from Standard Input in the following format:

L R

Output

Print the minimum possible value of (i \times j) \mbox{ mod } 2019 when i and j are chosen under the given condition.

Sample Input 1

2020 2040

Sample Output 1

2

When (i, j) = (2020, 2021), (i \times j) \mbox{ mod } 2019 = 2.

Sample Input 2

4 5

Sample Output 2

20

We have only one choice: (i, j) = (4, 5).

Solution in Ruby (2.3.3) (judge verdict: Wrong Answer)

l,r = gets.split.map(&:to_i)

if l*r < 2019
  puts l*(l+1)
else
  if l <= 2019 and 2019 <= r
    puts 0
  else
    # 2019以下
    if r < 2019
      ama = 2019 / l
      if l <= ama and ama < r
        puts l*(ama+1)%2019
      else
        puts l*(l+1)%2019
      end
    # 2019以上
    else
      a = l / 2019
      am = l % 2019
      b = r / 2019
      bm = r % 2019
      if am == 0 or bm == 0
        puts 0
      elsif a != b
        puts 0
      else
        puts l*(l+1)%2019
      end
    end
  end
end