Codeforces Round #418 (Div. 2) D. An overnight dance in discotheque

#include <iostream>  
#include <stdio.h>  
#include <string.h>   
#include <stack>  
#include <queue>   
#include <map>  
#include <set>  
#include <vector>  
#include <math.h>  
#include <bitset>  
#include <algorithm>  

using namespace std;

#define X first
#define Y second
#define eps  1e-2
#define gcd __gcd
#define pb push_back
#define PI acos(-1.0)
#define lowbit(x) (x)&(-x)
#define bug printf("!!!!!\n");
#define mem(x,y) memset(x,y,sizeof(x))

typedef long long LL;
typedef long double LD;
typedef pair<int,int> pii;
typedef unsigned long long uLL;

const int N = 1e5+2;
const int INF  = 1<<30;
const int mod  = 1e9+7;

int n;
struct  node
{
    double x,y,r;
    int times;
    bool operator <(const node &b) const {
        return (x-b.x)*(x-b.x)+(y-b.y)*(y-b.y)<b.r*b.r&&r<b.r;
    }
}p[N];
double getd(node a){
    return a.r*a.r*PI;
}
void solve(){
    scanf("%d",&n);
    for(int i=1;i<=n;i++){
        double x,y,r;scanf("%lf%lf%lf",&x,&y,&r);
        p[i]={x,y,r};
    }
    double ans=0;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            if(i!=j){
                if(p[i]<p[j]) p[i].times++;
            }
        }
    }
    for(int i=1;i<=n;i++){
        // cout<<p[i].times<<" "<<i<<endl;
        if(p[i].times==0||p[i].times&1) ans+=getd(p[i]);
        else ans-=getd(p[i]);
    }
    printf("%0.9lf\n",ans);
    return;
}

int main()
{
//    freopen("in.txt","r",stdin);
//    freopen("out.txt","w",stdout);
//    ios::sync_with_stdio(false);
    int t = 1;
    //scanf("%d",&t);
    while(t--){
    //    printf("Case %d: ",cas++);
        solve();
    }
    return 0;
}