下面有关函数的嵌套错在什么地方啊，我试了很久也没试出来，请大家帮我看看
#include "math.h"
main()
{long n;long sq(long),cub(long);
printf ("please input N:\n");
scanf ("%ld",&n);
printf ("sq is %ld\n",sq(n));
printf ("cub is %ld\n",cub(n));
getch();}

long sq(n)
long n;
{long a;a=n*n;return(a);}
long cub(long m);
{long b;b=sq(m)*m;return(b);}

long sq(long n)
{long a;a=n*n;return(a);}
long cub(long m)
{long sq(long);long b;b=sq(m)*m;return(b);}
main()
{long n;
printf ("please input N:\n");
scanf ("%ld",&n);
printf ("sq is %ld\n",sq(n));
printf ("cub is %ld\n",cub(n));

getch();
}