Cod sursa(job #937259)

Utilizator OpportunityVlad Negura Opportunity Data 10 aprilie 2013 00:22:48
Problema Aria Scor 0
Compilator cpp Status done
Runda Arhiva educationala Marime 0.34 kb
Raporteaza aceasta sursa 
#include <fstream>
using namespace std;

ifstream fi("aria.in");
ofstream fo("aria.out");

struct point{long long x,y;}a[1000000];

long long n,i;

int main(){
	
	fi >> n;
	for (i=1; i<=n; i++) fi >> a[i].x >> a[i].y;
	a[n+1]=a[1];
	long rs=0;
	for (i=1; i<=n; i++) rs+=(a[i].x*a[i+1].y-a[i+1].x*a[i].y);
	fo << rs/2;
	return 0;
}