Each unit square of 2020×2020 grid is painted into either red or white colour. Suppose that among four unit squares belonging to the intersection of any two lines any any two columns there are two same-coloured unit squares lying in the same line or in the same column. Find the minimal possible value of the total number of mono-coloured lines and columns.
Correct Solutions by,
- Toshihiro Shimizu, Kawasaki, Japan
- Magnus Jakobsson, Lund, Sweden
- Sena Başaran, İstanbul Erkek Lisesi
- Emirhan Yağcıoğlu, Özel Ankara Matematik ve Fen Bilimleri Anadolu Lisesi
- Roger Bengtsson, Lund, Sweden