#include <bits/stdc++.h>
#define eps 1e-10

using namespace std;

long double Hypot(int x, int y)
{
    return sqrt((long double)(1ll * x * x + 1ll * y * y));
}

const int N = 5e5 + 5;

pair<int, int> operator - (pair<int, int> x, pair<int, int> y)
{
    return make_pair(x.first - y.first, x.second - y.second);
}

long long operator * (pair<int, int> x, pair<int, int> y)
{
    return 1ll * x.first * y.second - 1ll * x.second * y.first;
}

double atan3(int y, int x)
{
    double f = atan2(y, x);
    return (f > -eps ? f : f + 2 * acos(-1.0));
}

int cs;

int cmp(pair<int, int> x, pair<int, int> y)
{
    double t1 = atan3(x.second, x.first) - atan3(y.second, y.first);
    return (fabs(t1) > eps ? t1 < 0 : ((Hypot(x.first, x.second) < Hypot(y.first, y.second)) ^ cs));
}

pair<int, int> jz;

int cmp2(pair<int, int> x, pair<int, int> y)
{
    return cmp(x - jz, y - jz);
}

int flag, S[N], top, vis[N];

pair< vector< pair<int, int> >, vector< pair<int, int> > > convex(vector< pair<int, int> > z)
{
    for (int i = 1; i < (int)z.size(); ++i) {
        if (z[i].second < z[0].second || (z[i].second == z[0].second && z[i].first < z[0].first)) {
            swap(z[0], z[i]);
        }
    }
    jz = z[0];
    sort(z.begin() + 1, z.end(), cmp2);
    S[top = 1] = 0;
    for (int i = 1; i < (int)z.size(); ++i) {
        while (top >= 2 && (z[S[top]] - z[S[top - 1]]) * (z[i] - z[S[top]]) < 0) {
            --top;
        }
        S[++top] = i;
    }
    for (int i = 0; i < (int)z.size(); ++i) {
        vis[i] = 0;
    }
    if (top <= 2) {
        flag = 0;
        return {{}, {}};
    }
    vector< pair<int, int> > S1, S2;
    for (int i = 1; i <= top; ++i) {
        S1.push_back(z[S[i]]);
        vis[S[i]] = 1;
        if ((z[S[i]] - z[S[(i == 1 ? top : i - 1)]]) * (z[S[(i == 1 ? top : i - 1)]] - z[S[(i == 1 ? top - 1 : (i == 2 ? top : i - 2))]]) == 0) {
            flag = 0;
            return {{}, {}};
        }
    }
    for (int i = 0; i < (int)z.size(); ++i) {
        if (!vis[i]) {
            S2.push_back(z[i]);
        }
    }
    return make_pair(S1, S2);
}

pair< vector< pair<int, int> >, vector< pair<int, int> > > convexHull(vector< pair<int, int> > z)
{
    cs = 0;
    pair< vector< pair<int, int> >, vector< pair<int, int> > > res1 = convex(z);
    if (!flag) {
        return {{}, {}};
    }
    cs = 1;
    pair< vector< pair<int, int> >, vector< pair<int, int> > > res2 = convex(z);
    if (!flag) {
        return {{}, {}};
    }
    return res1;
}

long double jerry(vector< pair<int, int> > z)
{
    long double res = 0;
    for (int i = 0; i < (int)z.size(); ++i) {
        int j = (i + 1 == (int)z.size() ? 0 : i + 1);
        res += Hypot(z[i].first - z[j].first, z[i].second - z[j].second);
    }
    return res;
}

signed main()
{
    int T;
    scanf("%d", &T);
    int DEBUG = 0;
    for (int test = 1; test <= T; ++test) {
        int n;
        scanf("%d", &n);
        vector< pair<int, int> > z;
        for (int i = 1, x, y; i <= n; ++i) {
            scanf("%d%d", &x, &y);
            DEBUG &= (test != 1 || i != 1 || x == -821105972);
            z.emplace_back(x, y);
        }
        if (DEBUG && test == 2743) {
            printf("%d\n", n);
            for (auto [x, y] : z) {
                printf("%d %d\n", x, y);
            }
        }
        flag = 1;
        z.emplace_back(0, 0);
        pair< vector< pair<int, int> >, vector< pair<int, int> > > tmp = convexHull(z);
        long double res = 0;
        if (flag) {
            vector< pair<int, int> > p1 = tmp.first, p2 = tmp.second, p3;
            int hv = 0;
            for (int i = 0; i < (int)p1.size(); ++i) {
                hv |= (p1[i] == make_pair(0, 0));
            }
            if (hv) {
                p2.emplace_back(0, 0);
                if ((int)p2.size() >= 3) {
                    tmp = convexHull(p2);
                    p2 = tmp.first, p3 = tmp.second;
                    if (flag && p3.empty()) {
                        res = max(res, jerry(p1) + jerry(p2));
                    }
                }
            }
        }
        z.pop_back();
        sort(z.begin(), z.end(), cmp);
        vector<int> hv;
        for (int i = 0; i < (int)z.size(); ++i) {
            if ((z[i] - z[(i + n - 1) % n]) * (z[(i + 1) % n] - z[i]) <= 0) {
                hv.push_back(i);
            }
        }
        if ((int)hv.size() > 4) {
            if (!DEBUG) {
                printf("%.10Lf\n", res);
            }
            continue;
        }
        int ok = 1;
        for (int i = 0; i < (int)z.size(); ++i) {
            int j = (i + 1) % n;
            if (z[i] * z[j] == 0 && ((z[i].first != 0 && z[j].first != 0 && (z[i].first > 0) == (z[j].first > 0)) || (z[i].first == 0 && z[j].first == 0 && (z[i].second > 0) == (z[j].second > 0)))) {
                ok = 0;
                break;
            }
        }
        if (!ok) {
            if (!DEBUG) {
                printf("%.10Lf\n", res);
            }
            continue;
        }
        long double ts = jerry(z);
        for (int i = 0, j = 1; i < (int)z.size(); ++i) {
            while ((j + 1) % n != i && (make_pair(0, 0) - z[i]) * z[(j + 1) % n] <= 0) {
                j = (j + 1) % n;
            }
            if ((make_pair(0, 0) - z[i]) * z[(j + 1) % n] == 0 || (make_pair(0, 0) - z[j]) * z[(i + 1) % n] == 0) {
                continue;
            }
            int ok = 1;
            for (auto x : hv) {
                if (x != i && x != j && x != (i + 1) % n && x != (j + 1) % n) {
                    ok = 0;
                    break;
                }
            }
            if (ok) {
                res = max(res, ts + Hypot(z[i].first, z[i].second)
                                  + Hypot(z[(i + 1) % n].first, z[(i + 1) % n].second)
                                  + Hypot(z[j].first, z[j].second)
                                  + Hypot(z[(j + 1) % n].first, z[(j + 1) % n].second)
                                  - Hypot(z[i].first - z[(i + 1) % n].first, z[i].second - z[(i + 1) % n].second)
                                  - Hypot(z[j].first - z[(j + 1) % n].first, z[j].second - z[(j + 1) % n].second));
            }
        }
        if (!DEBUG) {
            printf("%.10Lf\n", res);
        }
    }
    return 0;
}