#include
int fan(int n)
{
int k;
if(n==0||n==1)
return 3;
else
k=n-fan(n-2);
return k;
}
int main()
{
printf("%d\n", fan(9));
return 0;
}
1、fun(9);
2、9-fun(7);
3、9-(7-fun(5));
4、9-(7-(5-fun(3)))
5、9-(7-(5-(3-fun(1)))) =>9-(7-(5-(3-3))) =7;