Problem A. 790. (December 2020)

A. 790. Andrew and Barry plays the following game: there are two heaps with \(\displaystyle a\) and \(\displaystyle b\) pebbles, respectively. In the first round Barry chooses a positive integer \(\displaystyle k\), and Andrew takes away \(\displaystyle k\) pebbles from one of the two heaps (if \(\displaystyle k\) is bigger than the number of pebbles in the heap, he takes away the complete heap). In the second round the roles are reversed: Andrew chooses a positive integer and Barry takes away the pebbles from one the two heaps. This goes on, in each round the two players are reversing the roles. The player that takes the last pebble loses the game.

Which player has a winning strategy?

Submitted by András Imolay, Budapest

(7 pont)

Deadline expired on January 11, 2021.

Statistics:

13 students sent a solution.
7 points:	Fleiner Zsigmond, Füredi Erik Benjámin, Horcsin Bálint, Kovács 129 Tamás, Sztranyák Gabriella, Varga Boldizsár, Várkonyi Zsombor.
4 points:	1 student.
2 points:	2 students.
1 point:	2 students.
0 point:	1 student.

Problems in Mathematics of KöMaL, December 2020