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 System.Text;
using System.Text.RegularExpressions;

namespace AtCoder
{
	public class Program
	{
		static void Main(string[] args)
		{
			int[] a = Console.ReadLine().Split().Select(p => int.Parse(p)).ToArray();
			int L = a[0];
			int R = a[1];

			if(R-L>= 2018)
			{
				// L〜Rの中に2019の倍数が含まれるので
				Console.WriteLine("0");
			}
			else
			{
				long ans = 2020;
				long ij = 0;
				for(int i=L; i<R; i++)
				{
					for(int j=i+1; j<=R; j++)
					{
						ij = (long)i*(long)j;
						if(ans > ij%2019)
							ans =  ij%2019;

						if (ans==0)
							break;
					}
					if(ans == 0)
						break;
				}
				Console.WriteLine(ans + "");
			}
		}
	}
}