[USACO07DEC]道路建设Building Roads

#include <cstdio>
#include <cmath>
#include <algorithm>
using namespace std;
int n,m,cnt;
double ans;
int x[1000005],y[1000005],fa[1000005];
struct Node{
    int x;
    int y;
    double dis;
}a[1000005];
inline int Find(int i){
    if(fa[i]==i)return i;
    return fa[i]=Find(fa[i]);
}
inline void Union(int x,int y){
    int f1=Find(x);
    int f2=Find(y);
    if(f1!=f2)fa[f1]=f2;
    return;
}
inline bool cmp(Node a,Node b){
    if(a.dis==b.dis)return a.x<b.x;
    return a.dis<b.dis;
}
int main(){
    scanf("%d%d",&n,&m);
    for(register int i=1;i<=n;i++)
        fa[i]=i;
    for(register int i=1;i<=n;i++)
        scanf("%d%d",&x[i],&y[i]);
    for(register int i=1;i<=n;i++)
        for(register int j=i+1;j<=n;j++){
            a[++cnt].x=i;
            a[cnt].y=j;
            a[cnt].dis=(double)sqrt((double)(x[i]-x[j])*(double)(x[i]-x[j])+(double)(y[i]-y[j])*(double)(y[i]-y[j]));
        }
    int x,y;
    for(register int i=1;i<=m;i++){
        scanf("%d%d",&x,&y);
        a[++cnt].x=x;
        a[cnt].y=y;
        a[cnt].dis=0.0;
    }
    sort(a+1,a+cnt+1,cmp);
    for(register int i=1;i<=cnt;i++){
        if(Find(a[i].x)!=Find(a[i].y)){
            Union(a[i].x,a[i].y);
            ans+=a[i].dis;
        }
    }
    printf("%.2lf\n",ans);
    return 0;
}