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 (1.42.0) (judge verdict: Accepted)

#[allow(unused_imports)]
use proconio::{fastout, input};

#[fastout]
fn main() {
    input!(l: usize, r: usize);
    let start = l % 2019;
    let end = start + if r - l > 2019 { 2019 } else { r - l };

    let mut ar = Vec::new();
    for i in start..end + 1 {
        ar.push(i);
    }

    let mut ans_min = 1 << 20;
    for i in 0..ar.len() {
        for j in i + 1..ar.len() {
            let v = (ar[i] * ar[j]) % 2019;
            if v < ans_min {
                ans_min = v;
            }
        }
    }

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