The Josephus problem is a theoretic problem occurring in computer science and mathematics.
There are n people standing in a circle waiting to be executed. After the first man is executed, k−1 people are skipped and the k-th man is executed. Then again, k−1 people are skipped and the k-th man is executed. The elimination proceeds around the circle (which is becoming smaller and smaller as the executed people are removed), until only the last man remains, who is given freedom.
The task is to choose the place in the initial circle so that you survive (remain the last one), given n and k.