//Nightmare05
#include<bits/stdc++.h>

using namespace std;

#define sp << " " <<
#define mod 1000000007
#define mp make_pair
#define pb push_back
#define int long long
#define double long double
#define INF (1e18+13)
#define PI 3.1415926535898

int power(int p,int j)
{
    int res=1;
    p=p%mod;
    while(j>0)
    {
        if(j&1)
            res=(res*p)%mod;
        j=j>>1;
        p=(p*p)%mod;
    }
    return res;
}


mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

int dice(int d,int p)
{
    uniform_int_distribution<int> uid(d,p);//specify l and s.
    return uid(rng) ;
}

double s(double m1,double m2,double c1,double c2,double c3,double c4)
{
    double x1,x2,x3,x4,y1,y2,y3,y4;
    x1=(c2-c1)/(m1-m2);
    x2=(c3-c2)/(m2-m1);
    x3=(c4-c3)/(m1-m2);
    x4=(c1-c4)/(m2-m1);
    y1=m1*x1+c1;
    y2=m2*x2+c2;
    y3=m1*x3+c3;
    y4=m2*x4+c4;
    double d[4];
    d[0]=(y2-y1)*(y2-y1)+(x2-x1)*(x2-x1);
    d[1]=(y3-y2)*(y3-y2)+(x3-x2)*(x3-x2);
    d[2]=(y4-y3)*(y4-y3)+(x4-x3)*(x4-x3);
    d[3]=(y1-y4)*(y1-y4)+(x1-x4)*(x1-x4);
    sort(d,d+4);
    if(abs(d[3]-d[0])<0.01)
        return sqrt((d[0]+d[3])/2)+26.0;
    else
        return -1;
}

int32_t main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    //freopen("elimination_validation_input.txt", "r", stdin);
    //freopen("output.txt", "w", stdout);
    int t;
    cin >> t;
    while(t--)
    {
        double dp=-1;
        double x1,x2,x3,x4,y1,y2,y3,y4;
        pair<double,double> a[4];
        cin >> a[0].first >> a[0].second >> a[1].first >> a[1].second >> a[2].first >> a[2].second >> a[3].first >> a[3].second;
        for(int j=0;j<6;j++)
        {
            if(j==1||j==3||j==5)
                swap(a[2],a[3]);
            if(j==2||j==4)
                swap(a[1],a[3]);
            x1=a[0].first;
            y1=a[0].second;
            x2=a[1].first;
            y2=a[1].second;
            x3=a[2].first;
            y3=a[2].second;
            x4=a[3].first;
            y4=a[3].second;
            for(double i=0.0;i<=1.0;i+=0.0001)
            {
                double m1=i*PI;
                m1=tan(m1);
                double c1=y1-m1*x1,c3=y3-m1*x3;
                double m2=-1/m1;
                if(m1==0.00000)
                    m2=tan(PI/2);
                double c2=y2-m2*x2,c4=y4-m2*x4;
                int h=1;
                double p[3];
                p[0]=y2-m1*x2-c1;
                p[1]=y3-m1*x3-c1;
                p[2]=y4-m1*x4-c1;
                if(abs(p[0])>abs(p[1])||abs(p[2])>abs(p[1]))
                    h=0;
                sort(p,p+3);
                for(int z=0;z<3;z++)
                    if(abs(p[z])<0.0000000001)
                        h=0;
                if(p[0]*p[2]<0)
                    h=0;
                p[0]=y1-m2*x1-c2;
                p[1]=y3-m2*x3-c2;
                p[2]=y4-m2*x4-c2;
                if(abs(p[0])>abs(p[2])||abs(p[1])>abs(p[2]))
                    h=0;
                sort(p,p+3);
                for(int z=0;z<3;z++)
                    if(abs(p[z])<0.0000000001)
                        h=0;
                if(p[0]*p[2]<0)
                    h=0;
                p[0]=y2-m1*x2-c3;
                p[1]=y1-m1*x1-c3;
                p[2]=y4-m1*x4-c3;
                if(abs(p[0])>abs(p[1])||abs(p[2])>abs(p[1]))
                    h=0;
                sort(p,p+3);
                for(int z=0;z<3;z++)
                    if(abs(p[z])<0.0000000001)
                        h=0;
                if(p[0]*p[2]<0)
                    h=0;
                p[0]=y2-m2*x2-c4;
                p[1]=y3-m2*x3-c4;
                p[2]=y1-m2*x1-c4;
                if(abs(p[1])>abs(p[0])||abs(p[2])>abs(p[0]))
                    h=0;
                sort(p,p+3);
                for(int z=0;z<3;z++)
                    if(abs(p[z])<0.0000000001)
                        h=0;
                if(p[0]*p[2]<0)
                    h=0;
                if(h)
                    dp=max(dp,s(m1,m2,c1,c2,c3,c4));
            }
        }
        if(dp<26)
            cout << -1 << endl;
        else
            cout << fixed << setprecision(2) << dp << endl;
    }
    return 0;
}