INF = 1 << 60
N = int(input())
A = list(map(int, input().split()))

dp = [[-INF] * 2 for _ in range(N+1)]
# dp[i][j]
# i : i 番目までみて
# j : 長さ j の部分列のときの j mod 2
# のスコアの最大値
dp[0][0] = 0
for i, a in enumerate(A):
    for j in range(2):
        dp[i+1][j] = dp[i][j]

    dp[i+1][1] = max(dp[i+1][1], -a)
    for j in range(2):
        k = (j+1) % 2
        sgn = 1 if k == 0 else -1
        dp[i+1][k] = max(dp[i+1][k], dp[i][j] + sgn * a)

ans = max(dp[N])
print(ans)