计算1！+2！+.....+20!的和

public class Sun {

public static void main(String[] args) {
long result = 0;
long sum = 1;
int i = 1;
for(i = 1; i <=20; i++)
{
sum = sum * i;
result += sum;
}

         System.out.println("result="+result);
}

}