题目如下:

import java.util.Scanner;

public class Demo_找出落单的那个数 {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		int a[] = new int[5];
		Scanner sc = new Scanner(System.in);
		for (int i = 0; i < a.length; i++) {
			a[i]=sc.nextInt();
		}
		
		//辅助数组来做,如果只出现一次,就是1喽
		int helper[] = new int[5];
		for (int i = 0; i < helper.length; i++) {
			helper[a[i]]++;
		}
		for (int i = 0; i < helper.length; i++) {
			if (helper[i]==1) {
				System.out.println(i);
			}
		}
	}

}