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: Accepted)

use std::io::*;

fn main() {
    let mut s: String = String::new();
    std::io::stdin().read_to_string(&mut s).ok();
    let mut itr = s.trim().split_whitespace();
    let l: u64 = itr.next().unwrap().parse().unwrap();
    let r: u64 = itr.next().unwrap().parse().unwrap();

    if r - l >= 2019 {
        println!("0");
    } else {
        let mut ans = 1u64 << 60;
        for i in l..r + 1 {
            for j in i + 1..r + 1 {
                ans = std::cmp::min(ans, i % 2019 * j % 2019);
            }
        }
        println!("{}", ans);
    }
}