#include <bits/stdc++.h>
#define ll long long
#define int long long
#define lowbit(x) ((x)&(-x))
using namespace std;

const int maxn = 105000;
const long double pi = acos(-1);
const long double eps = 1e-12;
//const long double inf = 2e9;

int n;
struct node
{
	int x,y;
	//friend long double operator *(const node &k1,const node &k2){ return k1.x*k2.x+k1.y*k2.y; }
}p[maxn];

pair<long double,int>a[maxn];
pair<long double,int>t[maxn];
int s[maxn];
void init()
{
	for(int i=1;i<=n;i++) s[i]=0;
}
void add(int x)
{
	for(;x<=n;x+=lowbit(x)) s[x]++;
}
int query(int x)
{
	int re=0;
	for(;x;x-=lowbit(x)) re+=s[x];
	return re;
}
int base;
int calc(long double mid)
{
	mid=mid-pi/2;
	long double k= tan(mid);
	
	for(int i=1;i<=n;i++)
	{
		a[i]=make_pair( p[i].x, 0 );
		t[i]=make_pair( p[i].y-k*p[i].x,i );
	}
	sort(t+1,t+n+1);
	
	for(int i=1;i<=n;i++) a[ t[i].second ].second=i;
	sort(a+1,a+n+1);
	
	init();
	int ret=0;
	for(int i=1;i<=n;)
	{
		int j=i;
		while(j<=n&&a[i].first==a[j].first)
		{
			ret+= (i-1)-query(a[j].second);
			j++;
		}
		while(i<j)
		{
			add(a[i].second);
			i++;
		}
	}
	return base+ret;
}
long double get_kth(int k)
{
	long double l=0,r= pi-eps;
	while(r-l>eps)
	{
		long double mid=(l+r)/2;
		int num= calc(mid);
		if(num>=k) r=mid;
		else l=mid;
	}
	return l;
}

signed main()
{
	ios_base::sync_with_stdio(false); ////////////////////////////////////////
	cin.tie(0);
	
	cin>>n;
	for(int i=1;i<=n;i++) 
	{
		cin>>p[i].x>>p[i].y;
		swap(p[i].x,p[i].y);
		p[i].y=-p[i].y;
	}
	
	base=0;
	map<int,int>mp;
	for(int i=1;i<=n;i++)
	{
		if(mp.count(p[i].x)>0) base+=mp[p[i].x];
		mp[p[i].x]++;
	}
	
	int N= n*(n-1)/2;
	long double ans;
	if(N%2==0) ans= ( get_kth(N/2)+get_kth(N/2+1) )/2;
	else ans= get_kth(N/2+1);
	
	cout<<fixed<<setprecision(12)<<ans<<endl;
	
	return 0;
}