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++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<n;i++)

using namespace std;
typedef long long ll;
typedef unsigned long ul;
typedef pair<ul, ul> P;

const int INF = 1e9;
const int MOD =1e9+7;
const ll LINF = 1e18;

int main(){
    int L, R;
    cin >> L >> R;

    int i=0, j= R - L;
    int min = INF;
    while (i < j)
    {
        ll tmp = ((L + i) * (L + j)) % 2019;
        if(tmp < min) {
            min = tmp;
        }else{
            j--;
        }
    }
    cout << min << endl;
}