import sys

int1 = lambda x: int(x) - 1

# input = lambda: sys.stdin.buffer.readline()
input = lambda: sys.stdin.readline().rstrip()
ii = lambda: int(input())
i1 = lambda: int1(input())
mi = lambda: map(int, input().split())
mi1 = lambda: map(int1, input().split())
li = lambda: list(mi())
li1 = lambda: list(mi1())
lli = lambda n: [li() for _ in range(n)]

INF = float("inf")
# mod = int(1e9 + 7)
mod = 998244353

n, k = mi()
a = li()

ok = 0
ng = int(1e15)
while ng - ok > 1:
    mid = ok + ng >> 1

    cnt = 0
    d = 0
    for i in range(n):
        if a[i] + d >= mid:
            continue
        c = (mid - (a[i] + d) + i) // (i + 1)
        cnt += c
        d += (i + 1) * c

    if cnt <= k:
        ok = mid
    else:
        ng = mid
print(ok)