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;
using System.Linq;

namespace ConsoleApp
{
    class Program
    {
        static void Main(string[] args)
        {
            var ss = Console.ReadLine().Split();
            var L = long.Parse(ss[0]);
            var R = long.Parse(ss[1]);

            if (R - L >= 2018)
            {
                Console.WriteLine(0);
                return;
            }

            var min = long.MaxValue;
            for (long i = L; i < R; i++)
            {
                for (long j = L + 1; j <= R; j++)
                {
                    long m = ((i % 2019) * ((i + 1) % 2019)) % 2019;
                    if (m < min)
                    {
                        min = m;
                    }
                }
            }

            Console.WriteLine(min);
        }
    }
}