ABC 139

6
-2 -3
10 -6
0 0
0 0
9 2
-7 0

9 2
-7 0
-2 -3
10 -6

9 2
-2 -3
10 -6
0 0
0 0
-7 0

struct Point {
    long long x, y;

    // 上半平面判定
    int is_up() const {
        if (y > 0) return 0;
        if (y == 0 && x > 0) return 0;
        return 1;
    }

    // 外積
    long long cross(const Point& other) const {
        return x * other.y - y * other.x;
    }

    // 内積
    long long dot(const Point& other) const {
        return x * other.x + y * other.y;
    }

    double norm() {
        return sqrt((double)this->norm2());
    }

    // ノルム^2
    long long norm2() const {
        return x * x + y * y;
    }

    Point operator+(const Point& other) const {
        return Point({x + other.x, y + other.y});
    }

    Point& operator+=(const Point& other) {
        this->x += other.x;
        this->y += other.y;
        return *this;
    }

    // 偏角ソート用 comparator
    // x 軸正方向から反時計回りに見たときの角度が小さい順
    // (0, 0) があるとバグる
    bool operator<(const Point& other) const {
        int h1 = is_up();
        int h2 = other.is_up();
        if (h1 != h2) return h1 < h2;
        return cross(other) > 0;
    }

    // ===== 角度計算 =====
    // this と other のなす角（0〜π, ラジアン）
    double angle(const Point& other) const {
        double d = (double)dot(other);
        double n = sqrt((double)norm2() * other.norm2());
        double c = d / n;

        return acos(clamp(c, -1.0, 1.0));
    }

    // 角度（度）
    double angle_deg(const Point& other) const {
        return angle(other) * 180.0 / M_PI;
    }
};

void solve() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    ll N;
    cin >> N;
    vector<Point> pts;
    rep(i, N) {
        ll x, y;
        cin >> x >> y;
        if (x == 0 && y == 0) continue;
        pts.emplace_back(x, y);
    }

    sort(all(pts));
    // for (auto [x, y] : pts) printf("%lld %lld\n", x, y);

    N = pts.size();
    rep(i, N) pts.push_back(pts[i]);

    ll norm_sq = 0;

    rep(i, N) {
        Point now = {0, 0};
        rep(j, N) {
            now += pts[i + j];
            chmax(norm_sq, now.norm2());
        }
    }
    printf("%.15lf\n", sqrt((double)norm_sq));
}