LET US XOR

Shaan and Hardik like discussing problems with each other. One day Shaan told his friend following problem: Given N points on a plane. Each point p is defined by it's two integer coordinates — pxand py. The distance between points a and b is min(|ax - bx|, |ay - by|). You should choose a starting point and make a route visiting every point exactly once, i.e. if we write down numbers of points in