#include <bits/stdc++.h>
using namespace std;
const int N = 510,eps = 1e-8;
#define x first
#define y second
typedef pair<double,double> PDD;
struct line{
    PDD st,ed;
}Line[N];
int q[N];
PDD pg[N],ans[N];
int n,m,cnt;

int sign(double x){
    if(fabs(x)<eps) return 0;
    if(x<0) return -1;
    return 1;
}

int dcmp(double x,double y){
    if(fabs(x-y)<eps) return 0;
    if(x-y<0) return -1;
    return 1;
}

double get_angle(line a){
    return atan2(a.ed.y-a.st.y,a.ed.x-a.st.x);
}



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

double dot(PDD a,PDD b){
    return a.x*b.x+a.y-b.y;
}

double cross(PDD a,PDD b){
    return a.x*b.y-a.y*b.x;
}

double area(PDD a,PDD b,PDD c){
    return cross(b-a,c-a);
}

bool cmp(line&a,line&b){
    double angle1 = get_angle(a),angle2 = get_angle(b);
    if(!dcmp(angle1,angle2)) return cross(a.ed-a.st,b.ed-a.st)<0;
    return angle1<angle2;
}


PDD get_insection(PDD p,PDD v,PDD q,PDD w){
    auto u = p-q;
    double t = cross(w,u)/cross(v,w);
    return {p.x+v.x*t,p.y+v.y*t};
}

PDD get_line_insection(line a,line b){
    return get_insection(a.st,a.ed-a.st,b.st,b.ed-b.st);
}

bool onright(line&a,line&b,line&c){
    auto o = get_insection(b.st,b.ed-b.st,c.st,c.ed-c.st);
    return sign(area(a.st,a.ed,o))<=0;
}

double half_plane_insection(){
    sort(Line,Line+cnt,cmp);
    int hh =0,tt =-1;
    for(int i =0;i<cnt;i++){
        if(i&&!dcmp(get_angle(Line[i]),get_angle(Line[i-1]))) continue;
        while(hh+1<=tt&&onright(Line[i],Line[q[tt-1]],Line[q[tt]])) tt--;
        while(hh+1<=tt&&onright(Line[i],Line[q[hh]],Line[q[hh+1]])) hh++;
        q[++tt] = i;
    }
    while(hh+1<=tt&&onright(Line[q[hh]],Line[q[tt]],Line[q[tt-1]])) tt--;
    while(hh+1<=tt&&onright(Line[q[tt]],Line[q[hh]],Line[q[hh+1]])) hh++;
    q[++tt] = q[hh];
    int k = 0;
    for(int i= hh;i+1<=tt;i++){
        ans[k++] = get_line_insection(Line[q[i]],Line[q[i+1]]);
    }
    double res = 0;
    for(int i = 0;i+1<k;i++){
        res+=area(ans[0],ans[i],ans[i+1]);
    }
    return res/2;
}


int main(){
    cin>>n;
    while(n--){
        cin>>m;
        for(int i = 0;i<m;i++) cin>>pg[i].x>>pg[i].y;
        for(int i = 0;i<m;i++){
            Line[cnt++] = {pg[i],pg[(i+1)%m]};
        }
    }
    double res =half_plane_insection();
    printf("%.3lf",res);
}