Given a positive integer n, what is the largest k such that
the numbers 1,2,...,n can be put into k boxes so that
the sum of the numbers in each box is the same?
[When
n = 8, the example {1,2,3,6},{4,8},{5,7} shows that
the largest k is at least 3.]
The smallest possible sum is n and the next smallest possible sum is n+1, since n must itself be in some box.