Java 代码

import java.util.Scanner;
import java.util.HashSet;

public class Main
{
    public static void main(String[] args)
    {
        Scanner cin = new Scanner(System.in);

        int n = cin.nextInt();
        HashSet s = new HashSet();

        for (int i = 0; i < n; i ++)
        {
            s.add(cin.nextInt());
        }

        System.out.println(s.size());
    }
}