编写函数fun,计算n!

#include <stdio.h>

double fun ( int n )
{ double result = 1.0 ;
/************found************/
if (n==0)
return 1.0 ;
while( n >1 && n < 170 )
/************found************/
result *= n--;
return result ;
}

main ( )
{ int n ;
printf("Input N:") ;
scanf("%d", &n) ;
printf("\n\n%d! =%lf\n\n", n, fun(n)) ;
}