Eddy's picture

#include<iostream>
#include<cstdio>
#include<queue>
#include<cmath>
#include<algorithm>
using namespace std;
int fa[105];
struct ***er
{
	double x, y;
}m[105];
struct ***
{
	int to,from;
	double len;
}ed[15000];
int find(int x)
{
	if (x != fa[x])
	{
		fa[x]= find(fa[x]);
	}
	return fa[x];
}
int cnt, n;
void add(int from, int to, double len)
{
	ed[cnt].len = len;
	ed[cnt].to = to;
	ed[cnt].from = from;
	cnt++;
}
void init()
{
	for (int s = 0; s <= 104; s++)
	{
		fa[s] = s;
	}
	cnt = 0;
}
double join(int a, int b)
{
	a = find(a);
	b = find(b);
	if (a!= find(b))
	{
		fa[a] = b;
		return 1;
	}
	return 0;
}
bool cmp(*** a, *** b)
{
	return a.len < b.len;
}
int main()
{
	ios::sync_with_stdio(false);
	while (cin >> n)
	{
		init();
		for (int s = 0; s < n; s++)
		{
			scanf("%lf%lf", &m[s].x, &m[s].y);
		}
		for (int s = 0; s < n; s++)
		{
			for (int e = s + 1; e < n; e++)
			{
				double a = m[s].x - m[e].x;
				double b = m[s].y - m[e].y;
				double len = sqrt(a*a + b*b);
				add(s, e, len);
				add(e, s, len);
			}
		}
		double ans = 0;
		sort(ed, ed + cnt, cmp);
		for (int s = 0; s < cnt; s++)
		{
			int a = ed[s].to;
			int b = ed[s].from;
			double c = join(a, b);
		//	cout << c <<" "<<ed[s].len<< endl;
			ans += c*ed[s].len;
		}
		printf("%.2lf\n", ans);
	}
	return 0;
}