#!/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
INF = 10 ** 9

# %%
N, M, *W = map(int, read().split())


# %%
dp00 = np.full(N + 2, -INF, np.int64)
dp01 = np.full(N + 2, -INF, np.int64)
dp10 = np.full(N + 2, -INF, np.int64)
dp11 = np.full(N + 2, -INF, np.int64)
dp00[0] = 0
dp11[1] = 0
for x in W:
    newdp00 = np.full_like(dp00, -INF)
    newdp01 = np.full_like(dp00, -INF)
    newdp10 = np.full_like(dp00, -INF)
    newdp11 = np.full_like(dp00, -INF)

    np.maximum(newdp00, dp00, out=newdp00)
    np.maximum(newdp00, dp01, out=newdp00)
    np.maximum(newdp01[1:], dp00[:-1], out=newdp01[1:])
    np.maximum(newdp01[1:], dp01[:-1] + x, out=newdp01[1:])

    np.maximum(newdp10, dp10, out=newdp10)
    np.maximum(newdp10, dp11, out=newdp10)
    np.maximum(newdp11[1:], dp10[:-1], out=newdp11[1:])
    np.maximum(newdp11[1:], dp11[:-1] + x, out=newdp11[1:])

    dp00 = newdp00
    dp01 = newdp01
    dp10 = newdp10
    dp11 = newdp11


# %%
answer = max(dp00[M], dp11[M + 1])
print(answer)