LG4196

#include<bits/stdc++.h>

using namespace std;

#define gc c=getchar()
#define r(x) read(x)
#define db double

template<typename T>
inline void read(T&x){
    x=0;T k=1;char gc;
    while(!isdigit(c)){if(c=='-')k=-1;gc;}
    while(isdigit(c)){x=x*10+c-'0';gc;}x*=k;
}

const db eps=1e-8;
const int N=505;

inline db sqr(db x){
    return x*x;
}

inline int dcmp(const db &x){
    if(fabs(x)<eps)return 0;
    return x>0?1:-1;
}

struct Point{
    db x,y;

    inline Point(){}
    inline Point(db _x,db _y):x(_x),y(_y){}

};

#define Vec Point

inline Vec operator +(const Vec &a,const Vec &b){
    return Vec(a.x+b.x,a.y+b.y);
}

inline Vec operator -(const Vec &a,const Vec &b){
    return Vec(a.x-b.x,a.y-b.y);
}

inline void operator +=(Vec &a,const Vec &b){
    a.x+=b.x,a.y+=b.y;
}

inline void operator -=(Vec &a,const Vec &b){
    a.x-=b.x,a.y-=b.y;
}

inline Vec operator *(const Vec &a,const db &b){
    return Vec(a.x*b,a.y*b);
}

inline Vec operator /(const Vec &a,const db &b){
    return Vec(a.x/b,a.y/b);
}

inline db Cross(const Vec &a,const Vec &b){
    return a.x*b.y-a.y*b.x;
}

inline db Angle(const Vec &a){
    return atan2(a.y,a.x);
}

struct Line{
    Point S,T;
    db theta;

    inline Line(){}
    inline Line(const Point &A,const Point &B):S(A),T(B),theta(Angle(B-A)){}
};

inline bool OnRight(const Line &a,const Point &A){
    return dcmp(Cross(a.T-a.S,A-a.S))==-1;
}

inline bool operator <(const Line &a,const Line &b){
    if(dcmp(a.theta-b.theta))return dcmp(a.theta-b.theta)==-1;
    return dcmp(Cross(a.T-a.S,b.S-a.S))==-1;
}

inline Point LineCross(const Line &a,const Line &b){
    Vec u=a.T-a.S;
    Vec v=b.T-b.S;
    Vec w=a.S-b.S;
    db t=Cross(w,v)/Cross(v,u);
    return a.S+u*t;
}

Line Q1[N];
Point Q2[N];

inline int Half(Line *A,int n,Point *B){
    sort(A+1,A+n+1);
    int head=0,tail=0;
    Q1[0]=A[1];
    for(int i=2;i<=n;++i){
        while(head<tail&&OnRight(A[i],Q2[tail-1]))--tail;
        while(head<tail&&OnRight(A[i],Q2[head]))++head;
        Q1[++tail]=A[i];
        Q2[tail-1]=LineCross(A[i],Q1[tail-1]);
    }
    while(head<tail&&OnRight(Q1[head],Q2[tail-1]))--tail;
    while(head<tail&&OnRight(Q1[head],Q2[head]))++head;
    Q2[tail]=LineCross(Q1[head],Q1[tail]);
    n=0;
    for(int i=head;i<=tail;++i)B[++n]=Q2[i];
    return n;
}

inline db Area(Point *A,int n){
    db sum=Cross(A[n],A[1]);
    for(int i=1;i<n;++i){
        sum+=Cross(A[i],A[i+1]);
    }
    return sum/2;
}

Point A[N];
Line B[N];

int main(){
//  freopen(".in","r",stdin);
//  freopen(".out","w",stdout);
    int n,tot=0;r(n);
    while(n--){
        int m;r(m);
        for(int i=1;i<=m;++i){
            int x,y;r(x),r(y);
            A[i]=Point(x,y);
        }
        for(int i=1;i<m;++i){
            B[++tot]=Line(A[i],A[i+1]);
        }
        B[++tot]=Line(A[m],A[1]);
    }
    n=Half(B,tot,A);
    printf("%.3lf",Area(A,n));
    return 0;
}