IKMC 2027 - Grades 11-12 - Self-study SET 1 - Thematic Batch 3 Question 22

Sam has the paper shape and a 2 × 2 square stencil shown. He places the stencil with its squares aligned with the paper squares. Each placement increases the value of every covered square by 1. All values initially are 0. After several placements, some values are smudged as shown. In how many ways can the smudged values be restored consistently?

Editorial note: The source prints “cách số” where “các số” is intended; the original is retained.