#!/usr/bin/env python3
# %%
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines


# %%
import numpy as np

# %%
N = int(readline())
A = np.array(read().split(), np.int64)

# %%
from_left = np.zeros(N + 1, np.int64)
from_left[1:] = (A[::2] - A[1::2]).cumsum()


# %%
from_right = np.zeros(N + 1, np.int64)
from_right[1:] = (A[::-1][::2] - A[::-1][1::2]).cumsum()
from_right = from_right[::-1]

# %%
answer = (from_left + from_right).max()
print(answer)