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 Rust (1.15.1) (judge verdict: Wrong Answer)

fn get_input() -> String {
    let mut word = String::new();
    std::io::stdin().read_line(&mut word).unwrap();
    word.trim().to_owned()
}

fn main() {
    let (l, r) = {
        let line = get_input();
        let mut split = line.split_whitespace();
        let l: i64 = split.next().unwrap().parse().unwrap();
        let r: i64 = split.next().unwrap().parse().unwrap();
        (l, r)
    };

    let mut ans = -1;
    for i in l..r {
        for j in i+1..r+1 {
            let be_ans = ans;
            let a = i * j % 2019;
            ans = if ans == -1 { a } else { std::cmp::min(ans, a) };

            if be_ans != ans {
                break;
            }

        }
    }
    println!("{}", ans);
}