#include <bits/stdc++.h>
#define whlie while
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
#define rep(i,N) for(int i = 0; i < (N); i++)
#define repr(i,N) for(int i = (N) - 1; i >= 0; i--)
#define rep1(i,N) for(int i = 1; i <= (N) ; i++)
#define repr1(i,N) for(int i = (N) ; i > 0 ; i--)
#define each(x,v) for(auto& x : v)
#define all(v) (v).begin(),(v).end()
#define sz(v) ((int)(v).size())
#define vrep(v,it) for(auto it = v.begin(); it != v.end(); it++)
#define vrepr(v,it) for(auto it = v.rbegin(); it != v.rend(); it++)
#define ini(...) int __VA_ARGS__; in(__VA_ARGS__)
#define inl(...) ll __VA_ARGS__; in(__VA_ARGS__)
#define ins(...) string __VA_ARGS__; in(__VA_ARGS__)
#define rand rng
using namespace std; void solve();
using ll = long long;
using vi = vector<int>;
using vl = vector<ll>;
using vvi = vector< vector<int> >;
constexpr int inf = 1001001001;
constexpr ll infLL = (1LL << 61) - 1;

struct IoSetupNya {IoSetupNya() { cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(15); cerr << fixed << setprecision(7);} } iosetupnya;
template<typename T, typename U> inline bool amin(T &x, U y) { return (y < x) ? (x = y, true) : false; }
template<typename T, typename U> inline bool amax(T &x, U y) { return (x < y) ? (x = y, true) : false; }
template<typename T, typename U> ostream& operator <<(ostream& os, const pair<T, U> &p) { os << p.first << " " << p.second; return os; }
template<typename T, typename U> istream& operator >>(istream& is, pair<T, U> &p) { is >> p.first >> p.second; return is; }
template<typename T> ostream& operator <<(ostream& os, const vector<T> &v) { int s = (int)v.size(); rep(i,s) os << (i ? " " : "") << v[i]; return os; }
template<typename T> istream& operator >>(istream& is, vector<T> &v) { for(auto &x : v) is >> x; return is; }
void in(){} template <typename T,class... U> void in(T &t,U &...u){ cin >> t; in(u...);}
void out(){cout << "\n";} template <typename T,class... U> void out(const T &t,const U &...u){ cout << t; if(sizeof...(u)) cout << " "; out(u...);}
template<typename T>void die(T x){out(x); exit(0);}
#ifdef NyaanDebug
  #include "NyaanDebug.h"
  #define trc(...) do { cerr << #__VA_ARGS__ << " = "; dbg_out(__VA_ARGS__);} while(0)
  #define trca(v,N) do { cerr << #v << " = "; array_out(v , N);cout << endl;} while(0)
  int main(){solve_dbg();}
#else
  #define trc(...)
  #define trca(...)
  int main(){solve();}
#endif

using P = pair<int,int>;
constexpr int MOD = 998244853;
//mt19937_64 rng(58);
unsigned int rng(){static unsigned int x=123456789,y=362436069,z=521288629,w=88675123;unsigned int t;t=(x^(x<<11));x=y;y=z;z=w; return( w=(w^(w>>19))^(t^(t>>8)) );}
inline double rand_d(){return double(rand()) / UINT32_MAX; }
template<typename T>inline T ceil(T a,T b){return (a + b - 1) / b;}
/////////

int N;
vector<P> v;
vi used;

// Simulated Annealing(焼きなまし法)
// 乱択アルゴリズムにより近似解を求めるアルゴリズム
double calc(){
  int x = 0 , y = 0;
  rep(i , N){
    if(used[i]) x += v[i].fi , y += v[i].se;
  }
  //trc(used , x , y);
  return double(x) * double(x) + double(y) * double(y);
};
auto SA(const clock_t start){
  const double start_temp = 10000.0;
  const double end_temp = -1000.0;
  double cur_temp = start_temp;
  const double limit = 0.15;
  double cur_time = 0.0;
  int times = 0;
  auto score = calc();
  decltype(score) nxt_score;
  int idx[3] , x;
  while(1){
    if(times % 1000 == 0){
      //trc(times , score , cur_temp , used);
      cur_time = double(clock() - start) / CLOCKS_PER_SEC;
      cur_temp = max(0.0 , start_temp + (end_temp - start_temp) * cur_time / limit );
      cur_temp = cur_temp * cur_temp;
      if(cur_time > limit) break;
    }
    times++;
    // 遷移
    x = rand() % min(3 , N) + 1;
    rep(i , x) {
      idx[i] = rand() % N;
      used[idx[i]] ^= 1;
    }
    // scoreの再計算
    nxt_score = calc();
    //trc(score , nxt_score);
    if( exp(double(nxt_score - score) / cur_temp) > rand_d() ){
      // スコアの更新
      score = nxt_score;
    }
    else{
      // 復元
      rep(i , x) used[idx[i]] ^= 1;
    }
  }
  // SA後の処理
  trc(times , score , used);
  return sqrt(score);
}

void solve(){
  in(N);
  v.resize(N);
  in(v);
  used.resize(N);
  double ans = 0.0;
  rep(t , 10){
    rep(i , N) used[i] = rand() % 2;
    auto start = clock();
    ans = max(ans , SA(start) );
  }
  out(ans);

}


Measured memory_bytes: 384