INF = 10 ** 18
n, k = map(int, input().split())
dp0 = [-INF] * (k + 1)
dp1 = dp0[:]
dp0[0] = 0
for x in map(int, input().split()):
    dp0, dp1 = list(map(max, dp0, dp1)), [-INF if i == 0 else dp0[i-1] + x for i in range(k + 1)]
if (n + 1) // 2 < k:
    print('Impossible')
else:
    print(max(dp0[k], dp1[k]))