#include <bits/stdc++.h>
using namespace std;

using ll = long long;
using Pi = pair<int, int>;
using Pl = pair<ll, ll>;
using vint = vector<int>;
using vvint = vector<vint>;
using vvvint = vector<vvint>;
using vdouble = vector<double>;
using vvdouble = vector<vdouble>;
using vvvdouble = vector<vvdouble>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vvvll = vector<vvll>;
using uint = unsigned int;
using ull = unsigned long long;

template<typename T> using uset = unordered_set<T>;
template<typename T1, typename T2> using umap = unordered_map<T1, T2>;

constexpr int INF = (1 << 30) - 1;
constexpr ll LLINF = 1LL << 60;
constexpr int dy[] = {1, 0, -1, 0, 1, -1, -1, 1};
constexpr int dx[] = {0, 1, 0, -1, 1, 1, -1, -1};
constexpr char el = '\n';
constexpr int mod = 1000000007;
constexpr int mod2 = 998244353;
template<typename T> T gcd(T a, T b) { return (b ? gcd(b, a % b) : a); }
template<typename T> T lcm(T a, T b) { return (a / gcd(a, b) * b); }
template<typename T1, typename T2>
inline bool chmin(T1 &a, T2 b) { return (a > b && (a = b, true)); }
template<typename T1, typename T2>
inline bool chmax(T1 &a, T2 b) { return (a < b && (a = b, true)); }
template<typename T>
bool isin(T y, T x, T h, T w) { return (0 <= y && 0 <= x && y < h && x < w); }
template<typename T>
bool isin1(T y, T x, T h, T w) { return (0 < y && 0 < x && y <= h && x <= w); }

template<typename T>
ostream& operator <<(ostream &os, vector<T> &v) {
	os << v[0];
	for (int i = 1; i < v.size(); i++) os << " " << v[i];
	return (os);
}

template<typename T>
istream& operator >>(istream &is, vector<T> &v) {
	for (auto &u : v) is >> u;
	return (is);
}

template<typename T1, typename T2>
istream& operator >>(istream &is, pair<T1, T2> &p) {
	return (is >> p.first >> p.second);
}

constexpr double EPS = 1e-11;
bool equals(double a, double b) { return (abs(a - b) < EPS); }

struct V2 {
	double x, y;
	V2(double x = 0, double y = 0) : x(x), y(y) {}
	
	V2 operator + (V2 p) const { return (V2(x + p.x, y + p.y)); }
	V2 operator - (V2 p) const { return (V2(x - p.x, y - p.y)); }
	V2 operator * (double r) const { return (V2(x * r, y * r)); }
	V2 operator / (double r) const { return (V2(x / r, y / r)); }
	
	double norm() const { return (sqrt(sqrNorm())); }
	double sqrNorm() const { return (x*x + y*y); }
	
	bool operator < (const V2 &p) const { 
		return (x != p.x ? x < p.x : y < p.y); 
	}
	bool operator == (const V2 &p) const {
		return (equals(x, p.x) && equals(y, p.y));
	}

	V2 rotate90() const { return (V2(y, -x)); }
	V2 normalized() const { return (*this / norm()); }

	double dot(const V2 &p) const { return (x*p.x + y*p.y); }
	double cross(const V2 &p) const { return (x*p.y - y*p.x); }
	double arg() const { return (atan2(y, x)); }
};

void Main() {
	int N; cin >> N;
	vector<pair<pair<double, V2>, int>> dats;
	for (int i = 0; i < N; i++) {
		double x, y; cin >> x >> y;
		if (equals(x, 0) && equals(y, 0)) continue;
		V2 dat = V2(x, y);
		dats.emplace_back(make_pair(dat.arg(), dat), i);
		dats.emplace_back(make_pair(dat.arg()+2*M_PI, dat), i);
	}
	
	sort(begin(dats), end(dats));
	
	double maxv = 0;
	N = dats.size();
	for (int i = 0; i < N; i++) {
		for (int j = i; j < N; j++) {
			if (i != j && dats[i].second == dats[j].second) break;
			V2 sum;
			for (int k = i; k <= j; k++) {
				//cout << k << " " << dats[k].first.first << endl;
				sum = sum + dats[k].first.second;
			}
			//cout << endl;
			chmax(maxv, sum.norm());
		}
	}

	cout << maxv << endl;	
}

int main() {
	cin.tie(0);
	ios::sync_with_stdio(0);
	cout << fixed << setprecision(20);
	Main();
	return (0);
}


Measured memory_bytes: 384