#include <iostream>

using namespace std;

struct point{
int x;
int y;
};
struct vect{
int a;
int b;
};
vect create(point A, point B){
vect v;
v.a =  B.x- A.x;
v.b = B.y - A.y;
return v;
}
void printVector(vect v){
cout <<"[" << v.a << "," << v.b << "]" << endl;
}
vect scalar(int k, vect v)
{
    vect z;
    z.a = k*v.a;
    z.b = k*v.b;
    return z;

}
int main(){
point A = {1,2};
point B = {4,-1};

vect z = create(A, B);
printVector(z);

z = scalar(2,z);
printVector(z);
return 0;
}