Problem 1. Determine all positive integers $n$ with the following property: the set $\{1, 2, \dots, 2n - 1, 2n\}$ can be partitioned into two disjoint sets $\mathcal{A}$ and $\mathcal{B}$ with $n$ elements each, such that the sum of the elements of $\mathcal{A}$ divides the sum of the elements of $\mathcal{B}$.
Solution 1Solution 1
Solution 2 Solution2
Solution 3 Solution3
Solution 4 Solution4
1st European Mathematical Olympiad (EMO 2026)
1. Европска Математичка Олимпијада (EMO 2026)