n=int(input())
a=[int(j) for j in input().split()]
from collections import deque
q=deque(a)
ans=0
for i in range(n):
    if q[0]-q[1]>q[-1]-q[-2]:
        ans+=q.popleft()
        ans-=q.popleft()
    else:
        ans+=q.pop()
        ans-=q.pop()
print(ans)