Find the coordinates of the fourth point of the parallelogram

Given are the (x,y) coordinates of the endpoints of two adjacent sides of a parallelogram. Find the (x,y) coordinates of the fourth point.

Input

Each line of input contains eight floating point numbers: the (x,y) coordinates of one of the endpoints of the first side followed by the (x,y) coordinates of the other endpoint of the first side, followed by the (x,y) coordinates of one of the endpoints of the second side followed by the (x,y) coordinates of the other endpoint of the second side. All coordinates are in meters, to the nearest mm. All coordinates are between -10000 and +10000.

Output

For each line of input, print the (x,y) coordinates of the fourth point of the parallelogram in meters, to the nearest mm, separated by a single space.

Sample Input

0.000 0.000 0.000 1.000 0.000 1.000 1.000 1.000
1.000 0.000 3.500 3.500 3.500 3.500 0.000 1.000
1.866 0.000 3.127 3.543 3.127 3.543 1.412 3.145

Sample Output

1.000 0.000
-2.500 -2.500
0.151 -0.398

The meaning of the question: Give you two adjacent sides of a parallelogram, let you find the coordinates of the fourth point. 
Analysis of ideas: a relatively basic computational geometry problem, as long as the vector sums of the vectors are 
　　　　equal, the positions of equal points can be solved There are 4 cases, which are 1 3, 1 4, 2 3, 2 4 respectively. 
Code example:

struct point
{
    double x, y;
    point(double _x=0, double _y=0):x(_x), y(_y){}
     
    // point - point = vector
    point operator-(const point &v){
        return point(x-v.x, y-v.y);
    }
 
};
 
int dcmp(double x){
    if (fabs(x)<eps) return 0;
    else return x<0?-1:1;
}
bool operator == (const point &a, const point &b){
    return (dcmp(a.x-b.x)==0 && dcmp(a.y-b.y)==0);
}
 
typedef point Vector; // Vector represents a vector

point p[10];

int main() {
    //freopen("in.txt", "r", stdin);
    //freopen("out.txt", "w", stdout);
    
    while(~scanf("%lf%lf", &p[1].x, &p[1].y)){
        for(int i = 2; i <= 4; i++) {
            scanf("%lf%lf", &p[i].x, &p[i].y);
        }
        
        if (p[2] == p[3]) {
            Vector v = p[4] - p[3];
            printf("%.3f %.3f\n", v.x+p[1].x, v.y+p[1].y);
        }
        if (p[2] == p[4]){
            Vector v = p[3] - p[4];
            printf("%.3f %.3f\n", v.x+p[1].x, v.y+p[1].y);
        }
        if (p[1] == p[3]){
            Vector v = p[4]-p[3];
            printf("%.3f %.3f\n", v.x+p[2].x, v.y+p[2].y);
        }
        if (p[1] == p[4]){
            Vector v = p[3] - p[4];
            printf("%.3f %.3f\n", v.x+p[2].x, v.y+p[2].y);
        }
    }
    return 0;
}