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

dp = [[-1<<60,-1<<60] for i in range(n+1)]
dp[0][1] = 0

flag = False
for i in range(n):
	if dp[i][1] <= dp[i][0]+a[i]:
		flag = True
	if dp[i][0] <= dp[i][0]+a[i]:
		flag = True
	dp[i+1][1] = max(dp[i][1],dp[i][0]+a[i])
	dp[i+1][0] = max(dp[i][0],dp[i][1]-a[i])

if flag == False:
	print(-min(a))
else:
	print(max(dp[-1]))