//#define NDEBUG
#include <cstddef>
#include <cstdint>
#include <iostream>
#include <vector>

namespace n91 {

  using i8 = std::int_fast8_t;
  using i32 = std::int_fast32_t;
  using i64 = std::int_fast64_t;
  using u8 = std::uint_fast8_t;
  using u32 = std::uint_fast32_t;
  using u64 = std::uint_fast64_t;
  using isize = std::ptrdiff_t;
  using usize = std::size_t;

  constexpr usize operator"" _z(unsigned long long x) noexcept {
    return static_cast<usize>(x);
  }

  class rep {
    const usize f, l;

  public:
    class itr {
      friend rep;
      usize i;
      constexpr itr(const usize x) noexcept : i(x) {}

    public:
      void operator++() noexcept { ++i; }
      constexpr usize operator*() const noexcept { return i; }
      constexpr bool operator!=(const itr x) const noexcept { return i != x.i; }
    };
    constexpr rep(const usize first, const usize last) noexcept
      : f(first), l(last) {}
    constexpr itr begin() const noexcept { return itr(f); }
    constexpr itr end() const noexcept { return itr(l); }
  };
  class revrep {
    const usize f, l;

  public:
    class itr {
      friend revrep;
      usize i;
      constexpr itr(usize x) noexcept : i(x) {}

    public:
      void operator++() noexcept { --i; }
      constexpr usize operator*() const noexcept { return i; }
      constexpr bool operator!=(const itr x) const noexcept { return i != x.i; }
    };
    constexpr revrep(usize first, usize last) noexcept : f(--first), l(--last) {}
    constexpr itr begin() const noexcept { return itr(l); }
    constexpr itr end() const noexcept { return itr(f); }
  };
  template <class T> using vec_alias = std::vector<T>;
  template <class T> auto md_vec(const usize n, const T& value) {
    return std::vector<T>(n, value);
  }
  template <class... Args> auto md_vec(const usize n, Args... args) {
    return std::vector<decltype(md_vec(args...))>(n, md_vec(args...));
  }
  template <class T> constexpr T difference(const T& a, const T& b) {
    return a < b ? b - a : a - b;
  }
  template <class T> T scan() {
    T ret;
    std::cin >> ret;
    return ret;
  }

} // namespace n91

#include <algorithm>
#include <cmath>
#include <iostream>
#include <tuple>
#include <utility>
#include <iomanip>

namespace n91 {

  void main_() {
    usize n = scan<usize>();
    struct point_type {
      i64 x, y;
      double arg() const { return std::atan2(y, x); }
    };
    std::vector<point_type> p(n);
    for (auto& e : p) {
      std::cin >> e.x >> e.y;
    }
    std::sort(p.begin(), p.end(), [](const auto& l, const auto& r) {
      return std::tie(r.x, r.y) < std::tie(l.x, l.y);
      });
    while (p.back().x == static_cast<i64>(0) &&
      p.back().y == static_cast<i64>(0)) {
      p.pop_back();
    }
    n = p.size();
    std::sort(p.begin(), p.end(),
      [](const auto& l, const auto& r) { return l.arg() < r.arg(); });
    i64 ans = static_cast<i64>(0);
    for (const auto i : rep(0_z, n+1_z)) {
      for (const auto j : rep(0_z, n+1_z)) {
        i64 x = static_cast<i64>(0), y = static_cast<i64>(0);
        if (i <= j) {
          for (const auto k : rep(i, j)) {
            x += p[k].x;
            y += p[k].y;
          }
        }
        else {
          for (const auto k : rep(i, n)) {
            x += p[k].x;
            y += p[k].y;
          }
          for (const auto k : rep(0_z, j)) {
            x += p[k].x;
            y += p[k].y;
          }
        }
        ans = std::max(ans, x * x + y * y);
      }
    }
    std::cout << std::setprecision(20) <<std::sqrt(static_cast<double>(ans)) << std::endl;
  }

} // namespace n91

int main() {
  n91::main_();
  return 0;
}


Measured memory_bytes: 256