#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cstring>
#include <cmath>
#include <limits>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <functional>
#include <iomanip>

using namespace std;

#ifdef LOCAL
#define eprintf(...) fprintf(stderr, __VA_ARGS__)
#else
#define eprintf(...) 42
#endif
using ll = long long;
using vll = std::vector<ll>;
using vvll = std::vector<vll>;
using vvvll = std::vector<vvll>;
#define reps(i, S, E) for (ll i = (S); i <= (E); i++)
#define rep(i, N) reps(i, 0, N-1)
#define deps(i, E, S) for (ll i = (E); i >= (S); i--)
#define dep(i, N) deps(i, N-1, 0)
const ll INF = 1LL << 60;
const int INF_INT = 1 << 30;

template<class T> inline bool chmax(T &a, T b) { if (a < b) { a = b; return true; }return false; }
template<class T> inline bool chmin(T &a, T b) { if (a > b) { a = b; return true; }return false; }
struct mll {
	static ll MOD;
	ll val;
	mll(ll v = 0) : val(v % MOD) { if (val < 0) val += MOD; }
	mll operator - () const { return -val; }
	mll operator + (const mll &b) const { return val + b.val; }
	mll operator - (const mll &b) const { return val - b.val; }
	mll operator * (const mll &b) const { return val * b.val; }
	mll operator / (const mll &b) const { return mll(*this) /= b; }
	mll operator + (ll b) const { return *this + mll(b); }
	mll operator - (ll b) const { return *this - mll(b); }
	mll operator * (ll b) const { return *this * mll(b); }
	friend mll operator + (ll a, const mll &b) { return b + a; }
	friend mll operator - (ll a, const mll &b) { return -b + a; }
	friend mll operator * (ll a, const mll &b) { return b * a; }
	mll &operator += (const mll &b) { val = (val + b.val) % MOD; return *this; }
	mll &operator -= (const mll &b) { val = (val + MOD - b.val) % MOD; return *this; }
	mll &operator *= (const mll &b) { val = (val*b.val) % MOD; return *this; }
	mll &operator /= (const mll &b) {
		ll c = b.val, d = MOD, u = 1, v = 0;
		while (d) {
			ll t = c / d;
			c -= t * d; swap(c, d);
			u -= t * v; swap(u, v);
		}
		val = val * u % MOD;
		if (val < 0) val += MOD;
		return *this;
	}
	mll &operator += (ll b) { return *this += mll(b); }
	mll &operator -= (ll b) { return *this -= mll(b); }
	mll &operator *= (ll b) { return *this *= mll(b); }
	mll &operator /= (ll b) { return *this /= mll(b); }
	bool operator == (const mll &b) { return val == b.val; }
	bool operator != (const mll &b) { return val != b.val; }
	bool operator == (ll b) { return *this == mll(b); }
	bool operator != (ll b) { return *this != mll(b); }
	friend bool operator == (ll a, const mll &b) { return mll(a) == b.val; }
	friend bool operator != (ll a, const mll &b) { return mll(a) != b.val; }
	friend ostream &operator << (ostream &os, const mll &a) { return os << a.val; }
	friend istream &operator >> (istream &is, mll &a) { return is >> a.val; }
	static mll Combination(ll a, ll b) {
		chmin(b, a - b);
		if (b < 0) return mll(0);
		mll c = 1;
		rep(i, b) c *= a - i;
		rep(i, b) c /= i + 1;
		return c;
	}
};
using vmll = std::vector<mll>;
using vvmll = std::vector<vmll>;
using vvvmll = std::vector<vvmll>;
using vvvvmll = std::vector<vvvmll>;

struct Fast {
	Fast() {
		cin.tie(0);
		ios::sync_with_stdio(false);
		cout << fixed << setprecision(std::numeric_limits<double>::max_digits10);
	}
} fast; //cin,cout�������̂��܂��Ȃ��{�����w��

ll mll::MOD = (ll)(1e9 + 7);// 998244353ll;


//AtCoder Beginner Contest 139 - F
const double PI = 3.141592653589793;

int main() {
	ll N;
	cin >> N;
	vll x(N);
	vll y(N);
	rep(i, N) {
		cin >> x[i] >> y[i];
	}

	ll step = 100000;
	double result = 0.0;

	rep(i, step) {
		double theta = 2.0 * PI * (double)i / (double)step;
		double ix = cos(theta);
		double iy = sin(theta);
		//eprintf("theta: %f, ix: %f, iy:%f\n", theta, ix, iy);
		ll sumX = 0;
		ll sumY = 0;

		rep(j, N) {
			double proj = ix * (double)x[j] + iy * (double)y[j];
			if (proj > 0.0) {
				sumX += x[j];
				sumY += y[j];
			}
		}

		chmax(result, sqrt((double)sumX * (double)sumX + (double)sumY * (double)sumY));
	}

	cout << result << endl;

	return 0;
}



//AtCoder Beginner Contest 131 - F
/*
struct UnionFind {
	vector<int> data;
	UnionFind(int sz) {
		data.assign(sz, -1);
	}
	bool unite(int x, int y) {
		x = find(x), y = find(y);
		if (x == y) return (false);
		if (data[x] > data[y]) swap(x, y);
		data[x] += data[y];
		data[y] = x;
		return (true);
	}
	int find(int k) {
		if (data[k] < 0) {
			return (k);
		}
		return (data[k] = find(data[k]));
	}
	int size(int k) {
		return (-data[find(k)]);
	}
};

struct LLPair {
	int i = 0;
	ll x = 0;
	ll y = 0;
	LLPair() {}
	LLPair(int i, ll x, ll y) {
		this->i = i;
		this->x = x;
		this->y = y;
	}
};

int main() {
	ll N;
	cin >> N;
	vector<LLPair> p(N);
	rep(i, N) {
		cin >> p[i].x;
		cin >> p[i].y;
		p[i].i = (int)i;
	}

	UnionFind uf((int)N);

	{
		std::sort(p.begin(), p.end(), [](const LLPair &a, const LLPair &b) {
			return a.x < b.x; //�~���ɂ���ɂ� > �Ƃ���
		});
		ll currX = -1;
		int currNode = -1;
		rep(i, N) {
			if (currX == p[i].x) {
				uf.unite(currNode, p[i].i);
			}
			else {
				currX = p[i].x;
				currNode = p[i].i;
			}
		}
	}

	{
		std::sort(p.begin(), p.end(), [](const LLPair &a, const LLPair &b) {
			return a.y < b.y; //�~���ɂ���ɂ� > �Ƃ���
		});
		ll currY = -1;
		int currNode = -1;
		rep(i, N) {
			if (currY == p[i].y) {
				uf.unite(currNode, p[i].i);
			}
			else {
				currY = p[i].y;
				currNode = p[i].i;
			}
		}
	}

	//find�����Ȃ獪�͕ς��Ȃ�
	map<int, int> mp;
	vector<vector<LLPair>> group(1, vector<LLPair>(0));
	int nextIndex = 1;
	rep(i, N) {
		int root = uf.find(p[i].i);
		if (mp[root] == 0) {
			mp[root] = nextIndex;
			group.push_back(vector<LLPair>(0));
			group[nextIndex].push_back(p[i]);
			nextIndex++;
		}
		else {
			group[mp[root]].push_back(p[i]);
		}
	}

	//rep(i, nextIndex) {
	//	int nodeCount = (int)group[i].size();
	//	eprintf("group: %lld\n", i);
	//	rep(j, nodeCount) {
	//		eprintf("%d ", group[i][j].i);
	//	}
	//	eprintf("\n"); 
	//}

	ll result = 0;

	rep(i, nextIndex) {
		ll nodeCount = group[i].size();

		std::sort(group[i].begin(), group[i].end(), [](const LLPair &a, const LLPair &b) {
			return a.x < b.x; //�~���ɂ���ɂ� > �Ƃ���
		});
		ll xCount = 0;
		ll currX = -1;
		rep(j, nodeCount) {
			if (group[i][j].x != currX) {
				xCount++;
				currX = group[i][j].x;
			}
		}
		
		std::sort(group[i].begin(), group[i].end(), [](const LLPair &a, const LLPair &b) {
			return a.y < b.y; //�~���ɂ���ɂ� > �Ƃ���
		});
		ll yCount = 0;
		ll currY = -1;
		rep(j, nodeCount) {
			if (group[i][j].y != currY) {
				yCount++;
				currY = group[i][j].y;
			}
		}

		result += (xCount * yCount - nodeCount);
	}

	cout << result << endl;

	return 0;
}
*/


//AtCoder Beginner Contest 127 - E
/*
int main() {
	mll N;
	cin >> N;
	mll M;
	cin >> M;
	mll K;
	cin >> K;

	mll sum = 0;
	rep(i, N.val) { 
		mll temp = 0;
		mll row = i;
		temp += (row * (row + 1) / 2);
		row = N - i - 1;
		temp += (row * (row + 1) / 2);

		rep(j, M.val) {
			sum += temp * M;
			mll col = j;
			sum += N * (col * (col + 1) / 2);
			col = M - j - 1;
			sum += N * (col * (col + 1) / 2);
		}
	}

	sum /= 2;

	mll result = sum * mll::Combination(N.val * M.val, K.val);
	result *= mll::Combination(K.val, 2);
	result /= mll::Combination(N.val * M.val, 2);

	cout << result;
}
*/

Measured memory_bytes: 384