Description：

Solution：

Code：

#include<algorithm>

#include<iostream>

#include<cstdlib>

#include<cstdio>

#include<cmath>

#include<cstring>

using namespace std;

int tot;

#define eps 1e-10

int n;

#define MAXN 1000

struct point

{

	double x,y;

	point(double x_ = 0.0,double y_ = 0.0){x = x_;y = y_;}

}p[MAXN];

typedef point vector;

vector operator + (vector a,vector b){return vector(a.x + b.x,a.y + b.y);}

vector operator - (vector a,vector b){return vector(a.x - b.x,a.y - b.y);}

vector operator * (vector a,double b){return vector(a.x * b,a.y * b);}

double dotmul(vector a,vector b){return a.x * b.x + a.y * b.y;}

double crossmul(vector a,vector b){return a.x * b.y - a.y * b.x;}

double angle(vector a){return atan2(a.y,a.x);}

bool equal(double x,double y){return fabs(x - y) < eps;}

int sign(double x){return (equal(x,0.0) ? 0 : (x < 0 ? -1 : 1));}

struct plane

{

	point p;vector v;

	plane(){};

	plane(point p_,vector v_){p = p_;v = v_;}

}pl[MAXN],q[MAXN];

int head,tail;

bool in(point p,plane k){return sign(crossmul(p - k.p,k.v)) >= 0;}

point intersection(plane a,plane b){return b.p + b.v * (crossmul(a.v,a.p - b.p) / crossmul(a.v,b.v));}

bool cmp(plane a,plane b){return angle(a.v) < angle(b.v);}

#define F 1000

#define N -1000

double HPI()

{

	pl[++n] = plane(point(N,N),vector(0,1));

	pl[++n] = plane(point(N,F),vector(1,0));

	pl[++n] = plane(point(F,F),vector(0,-1));

	pl[++n] = plane(point(F,N),vector(-1,0));

	sort(pl + 1,pl + 1 + n,cmp);

	int n0 = 0;

	for(int i = 1;i <= n;++i)

	{

		if(n0 == 0)pl[++n0] = pl[i];

		else if(!equal(angle(pl[n0].v),angle(pl[i].v)))pl[++n0] = pl[i];

		else if(in(pl[i].p,pl[n0]))pl[n0] = pl[i];

	}

	n = n0;head = 1;tail = 2;

	q[1] = pl[1];q[2] = pl[2];

	for(int i = 3;i <= n;++i)

	{

		while(head < tail && !in(intersection(q[tail],q[tail - 1]),pl[i]))--tail;

		while(head < tail && !in(intersection(q[head],q[head + 1]),pl[i]))++head;

		if(head == tail && sign(crossmul(q[head].v,pl[i].v)) <= 0)return 0;

		q[++tail] = pl[i];

	}

	while(head < tail && !in(intersection(q[tail],q[tail - 1]),q[head]))--tail;

	int m = tail - head + 1;

	for(int i = 1;i < m;++i)p[i] = intersection(q[head + i],q[head + i - 1]);

	p[0] = p[m] = intersection(q[head],q[tail]);

	double res = 0.0;

	for(int i = 0;i < m;++i)res += crossmul(p[i],p[i + 1]);

	return res * 0.5;

}

point ps[51];

int main()

{

	scanf("%d",&tot);

	n = 0;

	int k;

	for(int i = 1;i <= tot;++i)

	{

		scanf("%d",&k);

		for(int j = 1;j <= k;++j)

		{

			cin >> ps[j].x >> ps[j].y;

		}

		for(int j = 2;j <= k;++j)

		{

			pl[++n] = plane(ps[j],ps[j - 1] - ps[j]);

		}

		pl[++n] = plane(ps[1],ps[k] - ps[1]);

	}

	printf("%.3lf\n",HPI());

	return 0;	

}