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: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using static System.Console;
using static System.Math;

class Program
{
    static void Main()
    {
        var LR = ReadLine().Split().Select(int.Parse).ToArray();
        var L = LR[0];
        var R = LR[1];
        var l = L % 2019;
        var r = R % 2019;
        var ans = R - L >= 2018 ? 0 : l > r ? 0 : 2018;
        for (var i = l; i <= r; i++)
        {
            for (var j = i + 1; j <= r; j++)
            {
                ans = Min(ans, i * j % 2019);
            }
        }
        WriteLine(ans);
    }
}