n = int(input())
A = list(map(int, input().split()))

from collections import deque
L = deque(A)
h = 0
t = 0
for i in range(n):
    #print(L)
    if i != n-1:
        l1 = L.popleft()
        l2 = L.popleft()
        r1 = L.pop()
        r2 = L.pop()
        if l1-l2 >= r1-r2:
            h += l1
            t += l2
            L.append(r2)
            L.append(r1)
        else:
            h += r1
            t += r2
            L.appendleft(l2)
            L.appendleft(l1)
    else:
        l = L.popleft()
        r = L.pop()
        if l >= r:
            h += l
            t += r
        else:
            h += r
            t += l
print(h-t)