function Vector(x, y)
    {
      this.x = x; 
      this.y = y; 
      
      this.equal = function(v)
      {
        return this.x == v.getX() && this.y == v.getY(); 
      }
      this.getX = function()
      {
        return this.x; 
      }
      this.getY = function()
      {
        return this.y; 
      }
      this.setX = function(x)
      {
        this.x = x; 
      }
      this.setY = function(y)
      {
        this.y = y; 
      }
      this.addX = function(x)
      {
        this.x += x; 
      }
      this.addY = function(y)
      {
        this.y += y; 
      }