#include <cstdio>#include <cstdlib>#include <cstring>#include <algorithm>#include <cmath>using namespace std;const double EPS = 1e-9;const int MAXN = 40;struct Point3  //空间点{    double x, y, z;    Point3( double x=0, double y=0, double z=0 ): x(x), y(y), z(z) { }    Point3( const Point3& a )    {        x = a.x;        y = a.y;        z = a.z;        return;    }    void showP()    {        printf("%f %f %f \n", x, y, z);    }    Point3 operator+( Point3& rhs )    {        return Point3( x+rhs.x, y+rhs.y, z+rhs.z );    }};struct Line3   //空间直线{    Point3 a, b;};struct plane3   //空间平面{    Point3 a, b, c;    plane3() {}    plane3( Point3 a, Point3 b, Point3 c ):        a(a), b(b), c(c) { }    void showPlane()    {        a.showP();        b.showP();        c.showP();        return;    }};double dcmp( double a ){    if ( fabs( a ) < EPS ) return 0;    return a < 0 ? -1 : 1;}//三维叉积Point3 Cross3( Point3 u, Point3 v ){    Point3 ret;    ret.x = u.y * v.z - v.y * u.z;    ret.y = u.z * v.x - u.x * v.z;    ret.z = u.x * v.y - u.y * v.x;    return ret;}//三维点积double Dot3( Point3 u, Point3 v ){    return u.x * v.x + u.y * v.y + u.z * v.z;}//矢量差Point3 Subt( Point3 u, Point3 v ){    Point3 ret;    ret.x = u.x - v.x;    ret.y = u.y - v.y;    ret.z = u.z - v.z;    return ret;}//两点距离double TwoPointDistance( Point3 p1, Point3 p2 ){    return sqrt( (p1.x - p2.x)*(p1.x - p2.x) + (p1.y - p2.y)*(p1.y - p2.y) + (p1.z - p2.z)*(p1.z - p2.z) );}//向量的模double VectorLenth( Point3 p ){    return sqrt( p.x*p.x + p.y*p.y + p.z*p.z );}//空间直线距离double LineToLine( Line3 u, Line3 v, Point3& tmp ){    tmp = Cross3( Subt( u.a, u.b ), Subt( v.a, v.b ) );    return fabs( Dot3( Subt(u.a, v.a), tmp ) ) / VectorLenth(tmp);}//取平面法向量Point3 pvec( plane3 s ){    return Cross3( Subt( s.a, s.b ), Subt( s.b, s.c ) );}//空间平面与直线的交点Point3 Intersection( Line3 l, plane3 s ){    Point3 ret = pvec(s);    double t = ( ret.x*(s.a.x-l.a.x)+ret.y*(s.a.y-l.a.y)+ret.z*(s.a.z-l.a.z) )/( ret.x*(l.b.x-l.a.x)+ret.y*(l.b.y-l.a.y)+ret.z*(l.b.z-l.a.z) );    ret.x = l.a.x + ( l.b.x - l.a.x ) * t;    ret.y = l.a.y + ( l.b.y - l.a.y ) * t;    ret.z = l.a.z + ( l.b.z - l.a.z ) * t;    return ret;}/************以上模板*************//*来自九野神的博*/