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.Collections.Generic;

public class CSharp
{
    public static void Main()
    {
        Kyopuro chokudai = new Kyopuro();
        chokudai.AtCoder();
    }
}

public class Kyopuro
{

    int L, R;

    public void AtCoder()
    {
        string[] input;
        input = Console.ReadLine().Split(' ');
        L = int.Parse(input[0]);
        R = int.Parse(input[1]);
        long ans = 0;
        if(R - L < 2019)
        {
            if((R % 2019) - (L % 2019) > 0)
            {
                ans = L % 2019;
                ans *= L + 1;
                ans %= 2019;
            }
        }

        Console.WriteLine(ans);
    }
    public static void DebugWL(object x) { System.Diagnostics.Debug.WriteLine(x); }
}