题意：略

思路：直接套用凸包模板

#include <iostream>

#include <cstdio>

#include <cmath>

#include <algorithm>

using namespace std;

#define N 50010

struct node{

	int x,y,d;

}p[N];

int dist(node a,node b){

	return (a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y);

}

int crossproduct(node a,node b,node c){

	return (b.x-a.x)*(c.y-a.y)-(c.x-a.x)*(b.y-a.y);

}

bool cmp1(node a,node b){

	return (a.x==b.x)?(a.y<b.y):(a.x<b.x);

}

bool cmp2(node a,node b){

	int cp=crossproduct(p[0],a,b);

	if(!cp)

		return a.d<b.d;

	return cp>0;

}

double Graham(int n){

	int i,j,k;

	sort(p,p+n,cmp1);

	for(i=1;i<n;i++)

		p[i].d=dist(p[0],p[i]);

	sort(p+1,p+n,cmp2);

	int top=1;

	for(i=2;i<n;i++){

		while(top>0&&crossproduct(p[i],p[top-1],p[top])<=0)

			--top;

		p[++top]=p[i];

	}

	p[++top]=p[0];

	int R=1,D=0;

	/*

	for(int L=0;L<top;++L){

		while(crossproduct(p[L],p[L+1],p[R])<crossproduct(p[L],p[L+1],p[R+1]))

			R=(R+1)%top;

		D=max(D,max(dist(p[L],p[R]),dist(p[L+1],p[R+1])));

	}

	*/

	double sum=0;

	for(i=0;i<top;i++)

		for(j=i+1;j<top;j++)

			for(k=j+1;k<top;k++)

			if(sum<crossproduct(p[i],p[j],p[k]))

				sum=crossproduct(p[i],p[j],p[k]);

	return sum*0.5;

}

int main(int argc, char** argv) {

	int n;

	while(scanf("%d",&n)!=EOF){

		for(int i=0;i<n;i++)

			scanf("%d%d",&p[i].x,&p[i].y);

		printf("%.2lf\n",Graham(n));

	}

	return 0;

}