Suppose the first player remove r matches (1 ≤ r < k )
from from one of the pile, leaving k − r matches in the pile.
I The second player then will remove the same number of
matches from the other pile.
I Now both piles have the same number of matches k − r
which is less than k.
I However from I.H. when both piles have the same number
of matches that is less than k, the second player will
always win.