from collections import deque
N=int(input())
A=deque(map(int, input().split()))
res=0
for i in range(N):
    a=A[0]-A[1]
    b=A[-1]-A[-2]
    if a>b:
        A.popleft()
        A.popleft()
        res+=a
    else:
        A.pop()
        A.pop()
        res+=b
print(res)