INF = 10**18
def chmax(DP,i,v):
    if DP[i] < v: DP[i] = v

def chmin(DP,i,v):
    if DP[i] > v: DP[i] = v

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

DP = [[-INF] * (2) for _ in range(N + 1)]
DP[0][0] = 0

for i in range(N):
    for j in range(2):
        if DP[i][j] == -INF:
            continue

        # 不採用
        chmax(DP[i + 1], j, DP[i][j])

        # 採用（ななめ）
        chmax(DP[i + 1], 1 - j, DP[i][j] + A[i]*(-1 if j == 0 else 1))

ans = max(DP[-1])
print(ans)