Question 75
Positive integers from $1$ to $n$ are written on the blackboard. The first player chooses a number and erases it. Then the second player chooses two consecutive numbers and erases them. After that the first player chooses three consecutive numbers and erases them. And finally the second player chooses four consecutive numbers and erases them. What is the smallest value of $n$ for which the second player can ensure that he completes both his moves?