## Solución al problema número 102501F de Codeforces - 102501F.

Cualquier duda no dudes en contactar.

``````
#include <bits/stdc++.h>
using namespace std;
#define EPS 1e-9
#define PI acos(-1.0)
typedef long long int ll;
struct point{
double x,y;
point(){x=y=0;}
point(int _x,int _y){x=_x,y=_y;}
bool operator <(point other) const{
if (fabs(x-other.x)>EPS)return x<other.x;
return y<other.y;
}bool operator ==(point other) const{
return (fabs(x-other.x)<EPS)&&
(fabs(y-other.y)<EPS);
}
point operator +(point other) const{
return point(x+other.x,y+other.y);
}point operator -(point other) const{
return point(x-other.x,y-other.y);
}
};

double calc_area(vector<point> Pa) {
double ans = 0;
for (int i = 0; i < (int) Pa.size() - 1; i++)
ans += Pa[i].x * Pa[i + 1].y - Pa[i].y * Pa[i + 1].x;
return fabs(ans) / 2.0;
}

int main(){
int cases; scanf("%d",&cases);
double area = 0;
while(cases--){
int points; scanf("%d",&points);
vector<point> V;
for(int i=0; i<points;i++){
int x,y; scanf("%d %d",&x,&y);
V.push_back(point{x,y});
}
V.push_back(V[0]);
area+=calc_area(V);
}
printf("%lld\n",(long long int)area);
}
``````