題目要求

題目分析

說不清楚，還是看程式碼吧

示例程式碼

import java.util.Scanner;
public class L1_013 {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int input = sc.nextInt();
		sc.close();
		int sum = 0;
		for(int i = 1; i <= input; i++) {
			int jiecheng = 1;
			for(int k = 1; k <= i; k++) {
				jiecheng *= k;
			}
			sum += jiecheng;
		}
		System.out.println(sum);
	}
}