输入一个正整数n，计算并输出n的阶乘

//fliename:Meiri.java
import java.util.Scanner;
  public class Meiri
{
   public static void main(String[]args)
{
   Scanner reader=new Scanner(System.in);
   int i,s=1,n=1,m=0;
   do{
        System.out.print("输入正整数");
       i=reader.nextInt();
       }while(i<=0);
       for(n=1;n<=i;n++)
 { s=s*n;
  m+=s;}
   System.out.println("Sum"+"="+m);
}}