#include <bits/stdc++.h>
using namespace std;
#define REP(i,n) for(int i=0;i<(int)(n);++i)
#define REPR(i,n) for (int i=(int)(n)-1;i>=0;--i)
#define FOR(i,c) for(__typeof((c).begin())i=(c).begin();i!=(c).end();++i)
#define ALL(c) (c).begin(), (c).end()
#define valid(y,x,h,w) (0<=y&&y<h&&0<=x&&x<w)
#define tpl(...) make_tuple(__VA_ARGS__)
const int INF = 0x3f3f3f3f;
const double EPS = 1e-8;
const double PI = acos(-1);
const int dy[] = {-1,0,1,0};
const int dx[] = {0,1,0,-1};
typedef long long ll;
typedef pair<int,int> pii;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
template<typename Ch,typename Tr,typename C,typename=decltype(begin(C()))>basic_ostream<Ch,Tr>& operator<<(basic_ostream<Ch,Tr>&os,
const C& c){os<<'[';for(auto i=begin(c);i!=end(c);++i)os<<(i==begin(c)?"":" ")<<*i;return os<<']';}
template<class S,class T>ostream&operator<<(ostream &o,const pair<S,T>&t){return o<<'('<<t.first<<','<<t.second<<')';}
template<int N,class Tp>void output(ostream&,const Tp&){}
template<int N,class Tp,class,class ...Ts>void output(ostream &o,const Tp&t){if(N)o<<',';o<<get<N>(t);output<N+1,Tp,Ts...>(o,t);}
template<class ...Ts>ostream&operator<<(ostream&o,const tuple<Ts...>&t){o<<'(';output<0,tuple<Ts...>,Ts...>(o,t);return o<<')';}
template<class T>void output(T t,char z=10){if(t<0)t=-t,putchar(45);int c[20];
int k=0;while(t)c[k++]=t%10,t/=10;for(k||(c[k++]=0);k;)putchar(c[--k]^48);putchar(z);}
template<class T>void outputs(T t){output(t);}
template<class S,class ...T>void outputs(S a,T...t){output(a,32);outputs(t...);}
template<class T>void output(T *a,int n){REP(i,n)cout<<a[i]<<(i!=n-1?',':'\n');}
template<class T>void output(T *a,int n,int m){REP(i,n)output(a[i],m);}
template<class T>bool input(T &t){int n=1,c;for(t=0;!isdigit(c=getchar())&&~c&&c-45;);
if(!~c)return 0;for(c-45&&(n=0,t=c^48);isdigit(c=getchar());)t=10*t+c-48;t=n?-t:t;return 1;}
template<class S,class ...T>bool input(S&a,T&...t){input(a);return input(t...);}
template<class T>bool inputs(T *a, int n) { REP(i,n) if(!input(a[i])) return 0; return 1;}

template<class T>
struct Pt {
  T x,y;
  Pt(T x=T(), T y=T()) :x(x),y(y) {}
  void in() {ll _x, _y; input(_x,_y); x=_x; y=_y; }
  bool operator<(const Pt &p) const { return x!=p.x?x<p.x:y<p.y; }
  bool operator==(const Pt &p) const { return x==p.x&&y==p.y; }
  Pt operator+=(const Pt &p) { x+=p.x, y+=p.y; return *this; }
  Pt operator-=(const Pt &p) { x-=p.x, y-=p.y; return *this; }
  Pt operator*=(const Pt &p) { T t=x;x=x*p.x-y*p.y,y=t*p.y+y*p.x; return *this;}
  Pt operator*=(const T &v) { x*=v; y*=v; return *this;}
  friend ostream& operator<<(ostream& os, const Pt &p) {return os<<'('<<p.x<<','<<p.y<<')';}
  friend istream& operator>>(istream& is, Pt &p) {return is>>p.x>>p.y;}

  Pt operator+(const Pt &p) const { return Pt(*this)+=p; }
  Pt operator-(const Pt &p) const { return Pt(*this)-=p; }
  Pt operator*(const Pt &p) const { return Pt(*this)*=p; }
  Pt operator*(const T &v) const { return Pt(*this)*=v; }
  friend Pt operator*(const T &v, const Pt &p) { return p*v; }
  bool operator!=(const Pt &p) const { return !(*this == p); }

  T abs() const { return hypot(x,y); }
  T norm() const { return x*x+y*y; }
  T arg() const { return atan2(y,x); }
  T dot(const Pt &p) const { return x*p.x+y*p.y; }
  T det(const Pt &p) const { return x*p.y-y*p.x; }
  friend T abs(const Pt &p) { return p.abs(); }
  friend T norm(const Pt &p) { return p.norm(); }
  friend T arg(const Pt &p) { return p.arg(); }
  friend T dot(const Pt &p, const Pt &q) { return p.dot(q); }
  friend T det(const Pt &p, const Pt &q) { return p.det(q); }
};

int sig(double r) {return r<-EPS?-1:r>EPS?1:0;}
int sig(ll r) {return r<0?-1:r>0?1:0;}
bool eq(double a, double b) {return sig(a-b)==0;}
bool eq(ll a, ll b) {return a==b;}

template<class T>int ccw(Pt<T> a, Pt<T> b, Pt<T> c); // 2(c--a--b), -2(a--b--c), 0(a=-c-=b)

template<> int ccw(Pt<ll> a, Pt<ll> b, Pt<ll> c) {
  b -= a; c -= a;
  return det(b,c) ? sig(det(b,c)) : dot(b,c)<0 ? 2 : (0<b.norm()&&b.norm()<c.norm()) ? -2 : 0;
}
template<> int ccw(Pt<double> a, Pt<double> b, Pt<double> c) {
  b -= a; c -= a;
  if (det(b,c)) return sig(det(b,c));
  if (sig(dot(b, c)) == -1) return +2; // c--a--b
  if (EPS < b.norm() && b.norm() < c.norm()-EPS) return -2; // a--b--c
  return 0;
}

template<typename _T>
struct Ln {
  typedef _T T;
  vector<Pt<T>> v;
  Ln(const Pt<T> &a, const Pt<T> &b) : v({a,b,b-a}) {}
  const Pt<T> operator[](int i) const { return v[i]; }
  void sub(const Pt<T> &p) { v[0] -= p; v[1] -= p; }
  int ccw(const Pt<T> &p) const { return ::ccw(v[0],v[1],p); }
};

template<typename _T>
struct Pg : public vector<Pt<_T> > {
  typedef _T T;
  Pg() {}
  Pg(int n) : vector<Pt<T>>(n) {}
  Pt<T> nxt(int i) const {return (*this)[i+1<(int)this->size()?(i+1):0];}
  Pt<T> dir(int i) const {return nxt(i)-(*this)[i];}
};

typedef Pt<ll> P;

// 時計回り側は含み、半時計回り側は含まない
int quadrant(const P &a) {
  double x = a.x, y = a.y;
  return x>0&&y>=0 ? 0 : x<=0&&y>0 ? 1 : x<0&&y<=0 ? 2 : 3;
}
// ロバストな角度比較
bool cmpAngle(const P &a, const P&b) {
  int p = quadrant(a);
  int q = quadrant(b);
  return p!=q ? p<q : det(a,b)>0;
}

int main() {
  int n;
  while (cin >> n) {
    vector<P> p;
    REP(i,n) {
      P a;
      cin >> a;
      if (a.x == 0 && a.y == 0) {
        continue;
      }
      p.push_back(a);
    }
    n = p.size();
    sort(ALL(p),cmpAngle);
    REP(i,n) p.push_back(p[i]);
    double ans = 0;
    for (int i=0; i<n; i++) {
      for (int j=i+1; j<=i+n; j++) {
        P a;
        for (int k=i; k<j; k++) {
          a += p[k];
        }
        chmax(ans, sqrt(a.norm()));
      }
    }
    printf("%.20f\n", ans);
  }
}


Measured memory_bytes: 256