Question 40
In a group of $n$ people, each one had a different ball. They performed a sequence of swaps; in each swap, two people swapped the ball they had at that moment. Each pair of people performed at least one swap. In the end each person had the ball he/she had at the start. Find the least possible number of swaps, if:
a) $n=5$;
b) $n=6$.
a) $n=5$;
b) $n=6$.