#include<bits/stdc++.h>
#define ll long long
#define vi vector<int>
#define vll vector<ll>
#define eb emplace_back
#define pb push_back
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
#define sz(v) ((int)v.size())
#define pii pair<int,int>
#define pll pair<ll,ll>
#define fi first
#define se second
#define umap unordered_map
#define uset unordered_set
#define mset multiset
#define ui unsigned int
#define ull unsigned ll
#define i128 __int128
using namespace std;

namespace qiqi {
	const double eps = 1e-10;
	int cmp(double x) {
		return x > eps ? 1 : x < -eps ? -1 : 0;
	}
	template<class T>
	struct Point {
		T x;
		T y;
		Point(T x_ = 0, T y_ = 0) : x(x_), y(y_) {}

		template<class U>
		operator Point<U>() {
			return Point<U>(U(x), U(y));
		}
		Point &operator+=(Point p) & {
			x += p.x;
			y += p.y;
			return *this;
		}
		Point &operator-=(Point p) & {
			x -= p.x;
			y -= p.y;
			return *this;
		}
		Point &operator*=(T v) & {
			x *= v;
			y *= v;
			return *this;
		}
		Point &operator/=(T v) & {
			x /= v;
			y /= v;
			return *this;
		}
		Point operator-() const {
			return Point(-x, -y);
		}
		friend Point operator+(Point a, Point b) {
			return a += b;
		}
		friend Point operator-(Point a, Point b) {
			return a -= b;
		}
		friend Point operator*(Point a, T b) {
			return a *= b;
		}
		friend Point operator/(Point a, T b) {
			return a /= b;
		}
		friend Point operator*(T a, Point b) {
			return b *= a;
		}
		friend bool operator==(Point a, Point b) {
			return a.x == b.x && a.y == b.y;
		}
		friend std::istream &operator>>(std::istream &is, Point &p) {
			return is >> p.x >> p.y;
		}
		friend std::ostream &operator<<(std::ostream &os, Point p) {
			return os << "(" << p.x << ", " << p.y << ")";
		}
	};

	template<class T>
	T dot(Point<T> a, Point<T> b) {
		return a.x * b.x + a.y * b.y;
	}

	template<class T>
	T cross(Point<T> a, Point<T> b) {
		return a.x * b.y - a.y * b.x;
	}

	struct BIT {
		int n; vi a;
		BIT(int n):n(n),a(n,0) {}
		int lbt(int x) {return x&(-x);}
		void upd(int x,int k) {
			for (int i = x+1; i <= n; i += lbt(i)) {
				a[i-1] += k;
			}
		}
		int qry(int x) {
			int k = 0;
			for (int i = x; i > 0; i -= lbt(i)) {
				k += a[i-1];
			}
			return k;
		}
	};

	using P = Point<double>;
	void main() {
		int n;
		cin >> n;
		vector<P> p(n);
		for (int i = 0; i < n; i++) {
			cin >> p[i];
		}
		auto calc = [&](double k) {
			ll res = 0;
			P q(cos(k),sin(k));
			vi o(n); iota(all(o),0);
			sort(all(o),[&](int a,int b) {
				return cmp(cross(q,p[b])-cross(q,p[a])) == 1;
			});
			vi rk(n);
			for (int i = 1; i < n; i++) {
				rk[o[i]] = rk[o[i-1]];
				if (cmp(cross(q,p[o[i]])-cross(q,p[o[i-1]])) == 1) {
					rk[o[i]]++;
				}
			}
			sort(all(o),[&](int a,int b) {
				return pair(p[a].y,-rk[a]) > pair(p[b].y,-rk[b]);
			});
			BIT bit(n);
			for (int i = 0; i < n; i++) {
				bit.upd(rk[o[i]],1);
				res += bit.qry(rk[o[i]]);
			}
			return res;
		};
		auto get = [&](ll k) {
			double l = 0,r = acos(-1);
			while (r-l > eps) {
				double mid = (l+r)/2;
				if (calc(mid) < k+1) {
					l = mid;
				}
				else {
					r = mid;
				}
			}
			return l;
		};
		ll m = 1ll*n*(n-1)/2;
		cout << (get(m/2)+get((m-1)/2))/2;
	}
}

int main() {
//	clock_t st = clock();
//	freopen("test.in","r",stdin);
//	freopen("test.out","w",stdout);
	ios::sync_with_stdio(false);
	cin.tie(nullptr);

	cout << fixed << setprecision(15);

	int T = 1;
//	cin >> T;
	while (T--) {
		qiqi::main();
	}

//	cout << (double)(clock()-st)/CLOCKS_PER_SEC;
	return 0;
}