#include<stdio.h>
int b[10]={1,3,5,6,8,9,13,14},a
int erfen (int x,int y)
{
	int o;
	if(x>y)
	return 0;
	else
	{
	  o=(x+y)/2;
	  if(b[o]==a) 
	  return 0;
	  if(a<b[o])  
	  return  erfen(x,o-1);
	  else return erfen(o+1,y);
	}
	return -1;
}
int main()
{
	int n,x=0,y=0;
	scanf("%d",&n)
	printf("%d",erfen(x,y));
	return 0;
	
	
}
原文:http://www.cnblogs.com/hxq2003/p/5651562.html