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 C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Windows;
using System.Collections.Generic;
using System.Linq;
using System.Numerics;

class Program
{
    static void Main(string[] args)
    {
      //入力を受け取る
      var LR = Console.ReadLine().Split(' ').Select(x => long.Parse(x)).ToArray();
      long L = LR[0];
      long R = LR[1];
      
      if(R-L+1 >= 2019){
        Console.WriteLine(0);
      }else if(L%2019 >= R%2019){
        Console.WriteLine(0);
      }else{
        var a = L%2019;
        var b = (L+1)%2019;
        Console.WriteLine(a*b);
      }
    }
}