// Original C++ solution (slower):
#pragma GCC optimize("Ofast")

#define _USE_MATH_DEFINES

#include "bits/stdc++.h"



using namespace std;



using u8 = uint8_t;

using u16 = uint16_t;

using u32 = uint32_t;

using u64 = uint64_t;

using i8 = int8_t;

using i16 = int16_t;

using i32 = int32_t;

using i64 = int64_t;



constexpr char newl = '\n';

constexpr double eps = 1e-10;



#define FOR(i,a,b) for (int i = (a); i < (b); i++)

#define F0R(i,b) FOR(i,0,b)

#define RFO(i,a,b) for (int i = ((b)-1); i >=(a); i--)

#define RF0(i,b) RFO(i,0,b)

#define fi first

#define se second

#define debug(x) cout << #x << ": " << x << '\n';

#define rng(a) a.begin(),a.end()

#define rrng(a) a.rbegin(),a.rend()



template<typename T1, typename T2> inline void chmin(T1& a, T2 b) { if (a > b) a = b; }

template<typename T1, typename T2> inline void chmax(T1& a, T2 b) { if (a < b) a = b; }

template<class T> void Print(vector<T> v) {

  F0R(i, v.size()) {

    cout << v[i] << ' ';

  }

  cout << newl;

}



#if 1



template<class T>

struct Vector2D {

  T X, Y;



  Vector2D(T x = 0, T y = 0) :X(x), Y(y) {}



  constexpr T MagnitudeSqr() const {

    return X * X + Y * Y;

  }



  constexpr T DistanceSqr(const Vector2D<T>& r) const {

    double a = r.X - X, b = r.Y - Y;

    return a * a + b * b;

  }



  constexpr double Distance(const Vector2D<T>& r) const {

    return sqrt(DistanceSqr(r));

  }



  Vector2D<T>& operator+=(const Vector2D<T>& r) {



    X += r.X;

    Y += r.Y;



    return *this;

  }



  friend Vector2D<T> operator+(Vector2D<T> l, const Vector2D<T>& r) {

    l += r;

    return l;

  }



  Vector2D<T>& operator-=(const Vector2D<T>& r) {



    X -= r.X;

    Y -= r.Y;



    return *this;

  }



  friend Vector2D<T> operator-(Vector2D<T> l, const Vector2D<T>& r) {

    l -= r;

    return l;

  }



  template<class N>

  Vector2D<T>& operator*=(const N& r) {



    X *= r;

    Y *= r;



    return *this;

  }



  template<class N>

  friend Vector2D<T> operator*(Vector2D<T> l, const N& r) {

    l *= r;

    return l;

  }



  template<class N>

  Vector2D<T>& operator/=(const N& r) {



    X /= r;

    Y /= r;



    return *this;

  }



  template<class N>

  friend Vector2D<T> operator/(Vector2D<T> l, const N& r) {

    l /= r;

    return l;

  }



  T DotProduct(const Vector2D<T>& r) const {

    return X * r.X + Y * r.Y;

  }



  Vector2D<T> Midpoint(const Vector2D<T>& r) const {

    return Vector2D<T>((X + r.X) / 2, (Y + r.Y) / 2);

  }



  // これが 0 のとき2つのベクトルは平行

  // （誤差を考え abs(perp) < eps という判定にした方が良い）

  T PerpProduct(const Vector2D<T>& r) const {

    return X * r.Y - Y * r.X;

  }



  static vector<Vector2D<T>> GetIntersectionOf2Lines(const Vector2D<T>& p1,

    const Vector2D<T>& v1, const Vector2D<T>& p2, const Vector2D<T>& v2,

    T eps = 1e-10) {



    T d = v1.PerpProduct(v2);



    if (Abs(d) < eps) {

      // 2つの線は平行



      // 重なっている場合は交点は存在することになるが、今回は省略

      return {};

    }



    auto w = p1 - p2;

    T si = v2.PerpProduct(w) / d;



    return { p1 + v1 * si };

  }



  friend constexpr ostream& operator << (ostream& os, const Vector2D<T>& x) noexcept {

    return os << x.X << ',' << x.Y;

  }

};



using ld = long double;



// INSERT ABOVE HERE

signed main() {

  cin.tie(0);

  ios_base::sync_with_stdio(false);



  cout << std::fixed << std::setprecision(15);



  int N;

  cin >> N;

  vector<Vector2D<ld>> vs(N);

  vector<ld> as(N);

  F0R(i, N) {

    cin >> vs[i].X >> vs[i].Y;

    as[i] = atan2(vs[i].Y, vs[i].X);

    //debug(as[i]);

  }



  ld result = 0;

  for (ld r = 0; r < M_PI * 2; r += 0.01) {

    Vector2D<ld> a(cos(r), sin(r)), b;



    F0R(i, N) {

      if (a.DotProduct(vs[i]) > 0) {

        b += vs[i];

      }

    }

    chmax(result, b.MagnitudeSqr());

  }



  cout << sqrt(result);

}

#endif


// Optimized solution to the same problem (faster):
#pragma GCC optimize("Ofast")

#define _USE_MATH_DEFINES

#include "bits/stdc++.h"



using namespace std;



using u8 = uint8_t;

using u16 = uint16_t;

using u32 = uint32_t;

using u64 = uint64_t;

using i8 = int8_t;

using i16 = int16_t;

using i32 = int32_t;

using i64 = int64_t;



constexpr char newl = '\n';

constexpr double eps = 1e-10;



#define FOR(i,a,b) for (int i = (a); i < (b); i++)

#define F0R(i,b) FOR(i,0,b)

#define RFO(i,a,b) for (int i = ((b)-1); i >=(a); i--)

#define RF0(i,b) RFO(i,0,b)

#define fi first

#define se second

#define debug(x) cout << #x << ": " << x << '\n';

#define rng(a) a.begin(),a.end()

#define rrng(a) a.rbegin(),a.rend()



template<typename T1, typename T2> inline void chmin(T1& a, T2 b) { if (a > b) a = b; }

template<typename T1, typename T2> inline void chmax(T1& a, T2 b) { if (a < b) a = b; }

template<class T> void Print(vector<T> v) {

  F0R(i, v.size()) {

    cout << v[i] << ' ';

  }

  cout << newl;

}



#if 1



template<class T>

struct Vector2D {

  T X, Y;



  Vector2D(T x = 0, T y = 0) :X(x), Y(y) {}



  constexpr T MagnitudeSqr() const {

    return X * X + Y * Y;

  }



  constexpr T DistanceSqr(const Vector2D<T>& r) const {

    double a = r.X - X, b = r.Y - Y;

    return a * a + b * b;

  }



  constexpr double Distance(const Vector2D<T>& r) const {

    return sqrt(DistanceSqr(r));

  }



  Vector2D<T>& operator+=(const Vector2D<T>& r) {



    X += r.X;

    Y += r.Y;



    return *this;

  }



  friend Vector2D<T> operator+(Vector2D<T> l, const Vector2D<T>& r) {

    l += r;

    return l;

  }



  Vector2D<T>& operator-=(const Vector2D<T>& r) {



    X -= r.X;

    Y -= r.Y;



    return *this;

  }



  friend Vector2D<T> operator-(Vector2D<T> l, const Vector2D<T>& r) {

    l -= r;

    return l;

  }



  template<class N>

  Vector2D<T>& operator*=(const N& r) {



    X *= r;

    Y *= r;



    return *this;

  }



  template<class N>

  friend Vector2D<T> operator*(Vector2D<T> l, const N& r) {

    l *= r;

    return l;

  }



  template<class N>

  Vector2D<T>& operator/=(const N& r) {



    X /= r;

    Y /= r;



    return *this;

  }



  template<class N>

  friend Vector2D<T> operator/(Vector2D<T> l, const N& r) {

    l /= r;

    return l;

  }



  T DotProduct(const Vector2D<T>& r) const {

    return X * r.X + Y * r.Y;

  }



  Vector2D<T> Midpoint(const Vector2D<T>& r) const {

    return Vector2D<T>((X + r.X) / 2, (Y + r.Y) / 2);

  }



  // これが 0 のとき2つのベクトルは平行

  // （誤差を考え abs(perp) < eps という判定にした方が良い）

  T PerpProduct(const Vector2D<T>& r) const {

    return X * r.Y - Y * r.X;

  }



  static vector<Vector2D<T>> GetIntersectionOf2Lines(const Vector2D<T>& p1,

    const Vector2D<T>& v1, const Vector2D<T>& p2, const Vector2D<T>& v2,

    T eps = 1e-10) {



    T d = v1.PerpProduct(v2);



    if (Abs(d) < eps) {

      // 2つの線は平行



      // 重なっている場合は交点は存在することになるが、今回は省略

      return {};

    }



    auto w = p1 - p2;

    T si = v2.PerpProduct(w) / d;



    return { p1 + v1 * si };

  }



  friend constexpr ostream& operator << (ostream& os, const Vector2D<T>& x) noexcept {

    return os << x.X << ',' << x.Y;

  }

};



using ld = long double;



// INSERT ABOVE HERE

signed main() {

  cin.tie(0);

  ios_base::sync_with_stdio(false);



  cout << std::fixed << std::setprecision(15);



  int N;

  cin >> N;

  vector<pair<Vector2D<ld>, ld>> vs(N);

  F0R(i, N) {

    cin >> vs[i].first.X >> vs[i].first.Y;

    vs[i].second = atan2(vs[i].first.Y, vs[i].first.X);

  }

  sort(rng(vs), [](const pair<Vector2D<ld>, ld>& l, const pair<Vector2D<ld>, ld>& r) {

    return l.second < r.second;

    });



  ld result = 0;

  F0R(i, N) {

    F0R(k, 4) {



      Vector2D<ld> b;

      ld end = vs[i].second + M_PI;

      end += (k & 2) ? eps : -eps;

      int j = i + (k & 1);

      if (j >= N) {

        j = 0;

        end -= M_PI * 2;

      }

      for (; vs[j].second < end; j++) {



        //debug(vs[j].first);

        b += vs[j].first;

        if (j == N - 1) {

          j = -1;

          end -= M_PI * 2;

        }

      }

      //cout << newl;

      chmax(result, b.MagnitudeSqr());

    }

  }



  cout << sqrt(result);

}

#endif


// Fastest known solution for this problem: