You are given an odd number n≥3. For every pair of integers (i,j) with 1≤i≤j≤n there is a domino, with i written on one its end and with j written on another (there are 2n(n+1) domino overall). Amin took this dominos and started to put them in a row so that numbers on the adjacent sides of the dominos are equal. He has put k dominos in this way, got bored and went away. After this Anton came to see this k dominos, and he realized that he can't put all the remaining dominos in this row by the rules. For which smallest value of k is this possible? Oleksii Masalitin IMEOcombinatoricsdominoes