def main():
    n = int(input())
    lst = list(map(int,input().split()))
    left = 0
    right = len(lst)-1
    answer = 0
    for _ in range(n):
        if (lst[left] - lst[left+1]) >= (lst[right] - lst[right-1]):
            answer += lst[left] - lst[left+1]
            left += 2
        else:
            answer += lst[right] - lst[right-1]
            right -= 2
    print(answer)





if __name__ == '__main__':
    main()