BdMO National 2016 Higher Secondary Problem 4:
Consider the set of integers {1,2,.........,100}. Let {x1,x2,.........,x100} be some arbitrary arrangement of the integers {1,2,.........,100}, where all of the xi are different. Find the smallest possible value of the sum,S=∣x2−x1∣+∣x3−x2∣+................+∣x100−x99∣+∣x1−x100∣.