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 Kotlin (1.0.0) (judge verdict: Wrong Answer)

import java.lang.Math.*


fun main(args: Array<String>) {
    val (l, r) = readDoubleList()
    val l2 = (l % 2019).toInt()
    val r2 = (r % 2019).toInt()
    var ans = 2019
    if (r2 <= l2 || r - l >= 2019 || l2 == 0) {
        println(0)
    } else {
        (r2 + 1).rep(l2, { i ->
            (r2 + 1).rep(l2, { j ->
                if (i == j) {
                } else {
                    ans = min(ans, (i * j) % 2019)
                }
            })
        })
    }
    println(ans)
}


fun readList() = readLine()!!.split(' ')
fun readIntList() = readList().map(String::toInt)
fun readLongList() = readList().map(String::toLong)
fun readDoubleList() = readList().map(String::toDouble)

fun readPair(): Pair<String, String> {
    val splite = readLine()!!.split(' ')
    return Pair(splite[0], splite[1])
}

fun <T> List<T>.copy() = this.map { it }

// 速度のためforEachは避ける
fun Int.rep(start: Int = 0, body: (Int) -> Unit) {
    for (i in start until this) {
        body(i)
    }
}

fun Long.rep(start: Long = 0, body: (Long) -> Unit) {
    for (i in start until this) {
        body(i)
    }
}

// 約数のList
fun divisor(value: Long): List<Long> {
    val max = sqrt(value.toDouble()).toLong()
    return (1..max)
        .filter { value % it == 0L }
        .map { listOf(it, value / it) }
        .flatten()
        .sorted()
}

// 範囲内の素数を取得
// fromだけ指定すると戻り値の個数で素数判定ができる
fun prime(from: Long, to: Long = from): List<Long> {
    return (from..to).filter { i ->
        val max = Math.sqrt(i.toDouble()).toLong()
        (2..max).all { j -> i % j != 0L }
    }
}

// 素因数分解
fun decom(value: Long): List<Long> {
    if (value == 1L) return listOf(1)
    val max = Math.sqrt(value.toDouble()).toLong()
    return prime(2, max).filter { value % it == 0L }
}

// 最大公約数
fun gcd(a: Long, b: Long): Long {
    return if (a % b == 0L) b else gcd(b, a % b)
}

// 文字列を入れ替え
fun swap(base: String, a: String, b: String): String {
    return base.map {
        when (it) {
            a.toCharArray()[0] -> b
            b.toCharArray()[0] -> a
            else -> it.toString()
        }
    }.joinToString()
}