题解 | #美妙的约会#

import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        ArrayList<Integer> arr = new ArrayList<>();
        int n = sc.nextInt();
        int n2 = n << 1;
        for(int i = 0; i < n2; i++) {
            arr.add(sc.nextInt());
        }
        int len = 0;
        while(arr.size() > 0) {
            int first = arr.get(0);
            arr.remove(0);
            int idx = arr.indexOf(first);
            len += idx;
            arr.remove(idx);
        }
        System.out.println(len);
    }
}