n, k = map(int, input().split())
a = list(map(int, input().split()))
b = bytes(i > 1 for i in a)
print(sum((sorted([
		sum(a[b.rfind(0, 0, k-1)-n:k-1]),
		sum(a[b.find(0, k):k-1:-1])
	])+[a[k-1]])[-1-a[k-1]:]))