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);
  }
  }