Two persons of masses $55\,\text{kg}$ and $65\,\text{kg}$ respectively, are at the opposite ends of a boat. The length of the boat is $3.0\,\text{m}$ and weighs $100\,\text{kg}$. The $55\,\text{kg}$ man walks up to the $65\,\text{kg}$ man and sits with him. If the boat is in still water the centre of mass of the system shifts by