Java求1+2!+3!+...+20!的和的代码

public class Ex21 {  static long sum = 0;  static long fac = 0;  public static void main(String[] args) {    long sum = 0;    long fac = 1;    for(int i=1; i<=10; i++) {    fac = fac * i;    sum += fac;    }    System.out.println(sum);  }  }