Determine for which positive integers
the set
can be partitioned into two disjoint subsets
and
such that the sum of the elements of
is equal to the sum of the elements of
%V0
Determine for which positive integers $k$ the set $$X = \{1990, 1990 + 1, 1990 + 2, \ldots, 1990 + k\}$$ can be partitioned into two disjoint subsets $A$ and $B$ such that the sum of the elements of $A$ is equal to the sum of the elements of $B.$