#include <bits/stdc++.h>
#pragma GCC diagnostic ignored "-Wsign-compare"
#pragma GCC diagnostic ignored "-Wsign-conversion"

#define NDEBUG
using i32 = int32_t;
using i64 = int64_t;
using u32 = uint32_t;
using u64 = uint64_t;
using uint = unsigned int;
using usize = std::size_t;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
template<typename T> constexpr T popcount(const T u) { return u ? static_cast<T>(__builtin_popcountll(static_cast<u64>(u))) : static_cast<T>(0); }
template<typename T> constexpr T log2p1(const T u) { return u ? static_cast<T>(64 - __builtin_clzll(static_cast<u64>(u))) : static_cast<T>(0); }
template<typename T> constexpr T msbp1(const T u) { return log2p1(u); }
template<typename T> constexpr T lsbp1(const T u) { return __builtin_ffsll(u); }
template<typename T> constexpr T clog(const T u) { return u ? log2p1(u - 1) : static_cast<T>(u); }
template<typename T> constexpr bool ispow2(const T u) { return u and (static_cast<u64>(u) & static_cast<u64>(u - 1)) == 0; }
template<typename T> constexpr T ceil2(const T u) { return static_cast<T>(1) << clog(u); }
template<typename T> constexpr T floor2(const T u) { return u == 0 ? static_cast<T>(0) : static_cast<T>(1) << (log2p1(u) - 1); }
template<typename T> constexpr bool btest(const T mask, const usize ind) { return ((static_cast<u64>(mask) >> ind) & static_cast<u64>(1)); }
template<typename T> constexpr T bcut(const T mask, const usize ind) { return ind == 0 ? static_cast<T>(0) : static_cast<T>((static_cast<u64>(mask) << (64 - ind)) >> (64 - ind)); }
template<typename T> bool chmin(T& a, const T& b) { return (a > b ? a = b, true : false); }
template<typename T> bool chmax(T& a, const T& b) { return (a < b ? a = b, true : false); }
constexpr unsigned int mod                  = 1000000007;
template<typename T> constexpr T inf_v      = std::numeric_limits<T>::max() / 4;
template<typename Real> constexpr Real pi_v = Real{3.141592653589793238462643383279502884};
template<typename T>
T read()
{
    T v;
    return std::cin >> v, v;
}
template<typename T>
std::vector<T> read_vec(const std::size_t size)
{
    std::vector<T> v(size);
    for (auto& e : v) { std::cin >> e; }
    return v;
}
template<typename... Types>
auto read_vals() { return std::tuple<std::decay_t<Types>...>{read<Types>()...}; }
#define SHOW(...) static_cast<void>(0)
template<typename T>
std::vector<T> make_v(const std::size_t size, T v) { return std::vector<T>(size, v); }
template<class... Args>
auto make_v(const std::size_t size, Args... args) { return std::vector<decltype(make_v(args...))>(size, make_v(args...)); }
int main()
{
    const auto n = read<usize>();
    std::vector<ll> x(n), y(n);
    std::vector<ld> s(n);
    for (usize i = 0; i < n; i++) { std::cin >> x[i] >> y[i], s[i] = (x[i] == 0 and y[i] == 0 ? 0 : std::atan2(y[i], x[i])); }
    std::vector<usize> ind(n);
    std::iota(ind.begin(), ind.end(), 0);
    std::sort(ind.begin(), ind.end(), [&](const usize i, const usize j) { return s[i] < s[j]; });
    std::vector<ll> sx(n), sy(n);
    for (usize i = 0; i < n; i++) { sx[i] = x[ind[i]], sy[i] = y[ind[i]]; }
    for (usize i = 1; i < n; i++) { sx[i] += sx[i - 1], sy[i] += sy[i - 1]; }
    const ld xx = sx[n - 1], yy = sy[n - 1];
    ld ans = 0;
    for (usize i = 0; i < n; i++) {
        for (usize j = i; j < n; j++) {
            ld xs = sx[j] - (i == 0 ? 0 : sx[i - 1]), ys = sy[j] - (i == 0 ? 0 : sy[i - 1]);
            chmax(ans, std::max(std::hypot(xs, ys), std::hypot(xx - xs, yy - ys)));
        }
    }
    std::cout << std::fixed << std::setprecision(48) << ans << std::endl;
    return 0;
}


Measured memory_bytes: 512