牛客算法：位运算

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
        String str;
        while ((str = bf.readLine()) != null) {
            boolean[] stu = new boolean[1001];
            StringBuilder sb = new StringBuilder();
            int n = Integer.parseInt(str);
            for (int i = 0; i < n; i++) {
                stu[Integer.parseInt(bf.readLine())] = true;
            }
            for (int i = 0; i < 1001; i++) {
                if (stu[i])
                    sb.append(i).append("\n");
            }
            sb.deleteCharAt(sb.length() - 1);
            System.out.println(sb.toString());
        }
    }
}

import java.util.*;
import java.io.*;

public class Main {
    public static void main(String[] args) throws Exception {
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        String s = in.readLine();
        int[] a = new int[128];
        int count = 0;
        for (int i = 0; i < s.length(); i++) {
            char b = s.charAt(i);
            if (a[b] == 0) {
                count++;
                a[b] = 1;
            }
        }
        System.out.println(count);
    }
}