#include<bits/stdc++.h>
using namespace std;
const int N=5000100;
int n,m,sum,cnt=1,fa[N];
double ans;
struct Node{
	int x;
	int y;
}Edge[N];
struct node{
	int from;
	int to;
	double value;
}edge[N];
double far(Node a,Node b){
	return (double)(sqrt((double)(a.x - b.x) * (a.x - b.x) + (double)(a.y - b.y) * (a.y - b.y)));
}
bool cmp(node x,node y){
	return x.value<y.value;
}
int find(int  x){return x==fa[x]?x:fa[x]=find(fa[x]);}
void kruskal(){
		for(int i=1;i<cnt;i++){
		int fx=find(edge[i].from);
		int fy=find(edge[i].to);
		if(fx!=fy){
			fa[fx]=fy;
			++sum;
			ans+=edge[i].value;
		}
		if(sum==n-1)return;
	}
}
signed main(){
	cin>>n>>m;
	for(int i=1;i<=n;i++){
		cin>>Edge[i].x>>Edge[i].y;
	}
	for(int i=1;i<=n;i++)fa[i]=i;
	for(int i=1;i<=n;i++){
		for(int j=i+1;j<=n;j++){
			edge[cnt++].from=i;
			edge[cnt].to=j;
			edge[cnt].value=far(Edge[i],Edge[j]);
		}
	}	
	for(int i=1;i<=m;i++){
		int u,v;
		cin>>u>>v;
		int count=0;
		count=(n+n-u+1)*(u-1)/2+v-u+1;
		edge[count].value=0; 
	}
	sort(edge+1,edge+cnt,cmp);
	kruskal();
	cout<<fixed<<setprecision(2)<<ans;
}

顶针盯了半天也没鉴定出来。

附：WA 0pts