#include<bits/stdc++.h>
using namespace std;
struct vec{
    double x, y;
    vec() {}
    vec(double a, double b) { x = a, y = b; }
    vec operator - (const vec &A){ return vec(x - A.x, y - A.y); }
};
struct Line{
    vec A, B; double polar;
    bool operator < (const Line &A)const{ return polar < A.polar; }
}linL, lpl[505], lpd[505];
const int eps = 1e-8;
vector<Line> L;
vector<vec> ans;
int n, m, l, r;

double cross(vec A, vec B){ return A.x * B.y - A.y * B.x; }
bool onleft(vec A, Line X){ return cross(X.B - X.A, A - X.A) > 0; }

vec inter(Line A, Line B){
    double s1, s2, k; vec ret;
    s1 = cross((A.B - A.A), (B.B - A.A));
    s2 = cross((B.A - A.A), (A.B - A.A));
    k = s2 / (s1 + s2);
    ret.x = B.A.x + k * (B.B.x - B.A.x); ret.y = B.A.y + k * (B.B.y - B.A.y);
    return ret;
}

inline void putit()
{
    int mx; vec p[55]; scanf("%d", &n);
    for(int i = 1; i <= n; ++i){
        scanf("%d", &mx);
        for(int j = 1; j <= mx; ++j) scanf("%lf%lf", &p[j].x, &p[j].y);
        for(int j = 1; j < mx; ++j){
            linL.A = p[j], linL.B = p[j + 1]; 
            linL.polar = atan2(linL.B.x - linL.A.x, linL.B.y - linL.A.y);
            L.push_back(linL);
        }
            linL.A = p[mx], linL.B = p[1]; 
            linL.polar = atan2(linL.B.x - linL.A.x, linL.B.y - linL.A.y);
            L.push_back(linL);      
    }
}

inline void HPI()
{
    sort(L.begin(), L.end());
    int len = L.size() - 1; 
    int siz = 1; lpd[1] = L[0];
    for(int i = 1; i <= len; ++i){
        if(L[i].polar != lpd[siz].polar) { lpd[++siz] = L[i]; continue; }
        if(onleft(L[i].A, lpd[siz])) lpd[siz] = L[i];
    }
    l = 1; r = 2; lpl[1] = lpd[1], lpl[2] = lpd[2];
    for(int i = 3; i <= siz; ++i){
        while(l < r && !onleft(inter(lpl[r], lpl[r - 1]), lpd[i])) r--;
        while(l < r && !onleft(inter(lpl[l], lpl[l + 1]), lpd[i])) l++;
        lpl[++r] = lpd[i];
    }
    while(l < r && !onleft(inter(lpl[r], lpl[r - 1]), lpl[l])) r--;
    while(l < r && !onleft(inter(lpl[l], lpl[l + 1]), lpl[r])) l++;
}

inline void print()
{
    lpl[r + 1] = lpl[l];
    for(int i = l; i <= r; ++i) ans.push_back(inter(lpl[i], lpl[i + 1]));
    if(ans.size() < 3) {printf("0.000"); return;}
    double ret = 0;     
    ans.push_back(ans[0]);
    int len = ans.size() - 1;
    for(int i = 0; i < len; ++i) 
    ret += cross(ans[i], ans[i + 1]);
    printf("%.3lf", fabs(ret) / 2);
}

int main()
{
    putit();
    HPI();
    print();
    return 0;
}