#include<stdio.h>
long fac(int n)
{
    long result;
    if(n==0||n==1)
    result=1;
    else
    {result=n*fac(n-1);
    return result;}
}
void main()
{
    int n;
    long f;
    printf("Please enter value of n:\n");
scanf("%d",&n);
if(n<=0)
printf("Sorry!You enter a wrong number!\n");
else
{f=fac(n);
printf("%d!=%ld\n",n,f);
}
}哪位大神来讲下具体过程啊

这要是输入个负数,不是就结束程序了 = = ,用goto接回去啊...