A classroom has N children with roll nos 1 to N. They are reading a story with P paragraphs. Supposing that the teacher starts with any random roll no R, and the students read sequentially what is the roll no of the last child to read?
We need to find the Roll no of last student which can be done by moving P-1 steps further from R.
Roll no of last student: R + P - 1
But since we are moving in a circle so we need to take mod of this summation with N
Because the Roll no starts from 1, so the roll no of the last student =(R -1 + P - 1) % N) + 1