n, k = map(int,input().split())
a = list(map(int,input().split()))

suki = 10 ** 18
kirai = 0
while suki - kirai > 1:
	targ = (suki + kirai) // 2
	tai = 0
	rrs = 0
	b = a[::]
	for i in range(n):
		b[i] += tai
		if b[i] < targ:
			g = (targ - b[i] + i) // (i + 1)
			tai += g * (i + 1)
			rrs += g
	if rrs > k:
		suki = targ
	else:
		kirai = targ

print(kirai)