Worms that are allowed to move one way
Source: Turkey TST 2014 Day 3 Problem 9
March 12, 2014
geometrycombinatoricsTSTcombinatorial geometryTurkey
Problem Statement
At the bottom-left corner of a chessboard, there are some green worms and at the top-left corner of the same chessboard, there are some brown worms. Green worms can move only to right and up, and brown worms can move only to right and down. After a while, the worms make some moves and all of the unit squares of the chessboard become occupied at least once throughout this process. Find the minimum total number of the worms.