c语言作业,编写程序：计算m!/(m-n)!,其中m、n为正整数且m>n

#include
long fun(long a);
void main()
{
long m,n;
printf("please input the 'm'\n");
scanf("%ld",&m);
printf("please input the 'n'\n");
scanf("%ld",&n);
printf("result=%ld\n",fun(m)*fun(n)/fun(m-n));
}
long fun(long a)
{
long result=1;
while(a)
result*=a--;
return result;
}