n = int(input())
A = list(map(int, input().split()))
dp = [[-10**18, -10**18] for i in range(n+1)]
dp[0][0] = 0
for i in range(n):
	for j in range(2):
		if j == 0:
			#次はマイナス
			dp[i+1][1] = max(dp[i+1][1], dp[i][j] - A[i])
			dp[i+1][j] = max(dp[i+1][j], dp[i][j])
		else:
			dp[i+1][0] = max(dp[i+1][0], dp[i][j] + A[i])
			dp[i+1][j] = max(dp[i+1][j], dp[i][j])
print(max(dp[n]))