точка и квадрат

#include <iostream>
#include <cmath>
#include <algorithm>
#include <iomanip>

using namespace std;

struct otrezok
{
  public:
  double x1, y1, x2, y2, x, y;
  double length;

  otrezok(double x1, double x2,double  y1,double y2)
  {
   length = sqrt((x2-x1)*(x2-x1) + (y2-y1)*(y2-y1));
  }
};

struct direct
{
 double a = 0, b = 0, c = 0;
 double parametr = INT16_MAX;
};

struct vershina
{
  double x, y;
};

direct storona (vershina first, vershina second)
{
  direct stright;
    stright.a = (first.y - second.y);
    stright.b = (second.x - first.x);
    stright.c =  first.x*second.y - second.x*first.y;
  return stright;
}

int main ()
{
  vershina A, B, C, D, X;
  cin >> A.x >> A.y >> B.x >> B.y >> C.x >> C.y >> D.x >> D.y;
  cin >> X.x >> X.y;

  direct AB = storona (A, B);
  direct BC = storona (B, C);
  direct CD = storona (D, C);
  direct DA = storona (A, D);
  // cout << BC.a << " " << BC.b << " " << BC.c << " ";
  double znach_1 = AB.a*X.x + AB.b*X.y + AB.c;
  double znach_2 = BC.a*X.x + BC.b*X.y + BC.c;
  double znach_3 = CD.a*X.x + CD.b*X.y + CD.c;
  double znach_4 = DA.a*X.x + DA.b*X.y + DA.c;
   //cout << znach_1 << znach_2 << znach_3 << znach_4;
  if (znach_1 <= 0 && znach_2 <= 0 && znach_3 >= 0 && znach_4 >= 0)
    cout << "Yes";
  else cout << "No";
}