10242 Fourth Point !!.cpp

#include <iostream>
#include <iomanip>
using namespace std;

int main()
{
    double x1, y1, x2, y2, x3, y3, x4, y4, x, y;

    cout << fixed;
    cout << setprecision(3);
    while (cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3 >> x4 >> y4)
    {
        if (x1 == x3 && y1 == y3)
        {
            x = x2 + x4 - x1;
            y = y2 + y4 - y1;
        }

        else if (x1 == x4 && y1 == y4)
        {
            x = x2 + x3 - x1;
            y = y2 + y3 - y1;
        }

        else if (x2 == x3 && y2 == y3)
        {
            x = x1 + x4 - x2;
            y = y1 + y4 - y2;
        }

        else
        {
            x = x1 + x3 - x2;
            y = y1 + y3 - y2;
        }

        cout << x << " " << y << endl;
    }
    return(0);
}