//T和Y的计划 
#include<iostream>
#include<iomanip>
#include<cmath>
#include <cfloat>
using namespace std;
#define max 5005

typedef struct
{
	double x, y, z;
}pos;

pos p[max];

int main()
{
	int n;
	cin >> n;
	pos acm, future, middle;
	double minDistance;
	int minPos; 
	double distance;
	for(int i = 0; i < n; i++)
		cin >> p[i].x >> p[i].y >> p[i].z;
	cin >> acm.x >> acm.y >> acm.z;
	cin >> future.x >> future.y >> future.z;
	middle.x = (acm.x + future.x) / 2;
	middle.y = (acm.y + future.y) / 2;
	middle.z = (acm.z + future.z) / 2;
	minDistance =  DBL_MAX; //#include<cfloat>有宏定义double最大值 
	for(int i = 0; i < n; i++)
	{
		distance = sqrt((middle.x - p[i].x)*(middle.x - p[i].x)
						+(middle.y - p[i].y)*(middle.y - p[i].y)+
						(middle.z - p[i].z)*(middle.z - p[i].z));
		if(distance < minDistance)
		{
			minDistance = distance;
			minPos = i;
		}
...