题解 | #小红的整数配对#

#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>

using namespace std;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    int n;
    long long k;
    cin >> n >> k;

    vector<long long> a(n);
    for (int i = 0; i < n; ++i) {
        cin >> a[i];
    }

    sort(a.begin(), a.end());

    long long score = 0;
    for (int i = n - 1; i > 0; ) {
        if (a[i] - a[i - 1] <= k) {
            score += a[i] * a[i - 1];
            i -= 2;
        } else {
            i -= 1;
        }
    }

    cout << score << endl;

    return 0;
}

import java.util.Scanner;
import java.util.Arrays;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        long k = sc.nextLong();

        long[] a = new long[n];
        for (int i = 0; i < n; i++) {
            a[i] = sc.nextLong();
        }

        Arrays.sort(a);

        long score = 0;
        for (int i = n - 1; i > 0; ) {
            if (a[i] - a[i - 1] <= k) {
                score += a[i] * a[i - 1];
                i -= 2;
            } else {
                i -= 1;
            }
        }

        System.out.println(score);
    }
}

def solve():
    n, k = map(int, input().split())
    a = list(map(int, input().split()))
    
    a.sort()
    
    score = 0
    i = n - 1
    while i > 0:
        if a[i] - a[i-1] <= k:
            score += a[i] * a[i-1]
            i -= 2
        else:
            i -= 1
            
    print(score)

solve()