https://www.google.com/books/edition/Singapore_Math_Challenge_Grades_5_8/2htqAgAAQBAJ?hl=en&gbpv=1&pg=PA57&printsec=frontcover
You have 85 beads
85/4 = 21*4 + 1
21/4 = 5*4 + 1
5/4 = 1* 4 + 1
