#include<bits/stdc++.h>
using namespace std;
const int N=50000+5;
struct Point{
    int x,y,z;
}point[N];
double acronym(int x1,int y1,int z1,int x2,int y2,int z2){
	return sqrt(pow(x1-x2,2)+pow(y1-y2,2)+pow(z1-z2,2));
}
bool cmp(Point x,Point y){
	return x.z>y.z;
}
int main(){
    int n;
    double ans=0;
    cin>>n;
    for(int i=0;i<n;i++){
        cin>>point[i].x>>point[i].y>>point[i].z;
    }
    sort(point,point+n,cmp);
	for(int i=1;i<n;i++){
		ans+=acronym(point[i].x,point[i].y,point[i].z,point[i-1].x,point[i-1].y,point[i-1].z);
	}
	printf("%3.f",ans);
	return 0;
}

各位大佬，求调，谢谢！！！