Java经典习题21

/*
题目：求1+2!+3!+...+20!的和
*/
public class Class21 {

public static void main(String[] args) {
int sum = 0;
int num = 1;
for(int i = 1; i <= 20; i++){
num = num * i;
sum = sum + num;
}
System.out.println(sum);
}
}