public Pair Add(Pair p1, Pair p2)
{
Pair result =new Pair();
result.First = p1.First + p2.First;
result.Second = p1.Second + p2.Second;
return result;
}
public Pair Substract(Pair p1, Pair p2)
{
Pair result=new Pair();
result.First = p1.First - p2.First;
result.Second = p1.Second - p2.Second;
return result;
}