from collections import deque

l, r = 0, 0
h, t = 0, 0
n = int(input())
A = deque(map(int, input().split()))
while A:
    l = A[0]-A[1]
    r = A[-1]-A[-2]
    if l >= r:
        h += A.popleft()
        t += A.popleft()
    else:
        h += A.pop()
        t += A.pop()
print(h-t)