import math


def is_ok(mi):
    s = 0
    l = 0
    for i in range(n):
        if a[i] + s < mi:
            m = math.ceil((mi - a[i] - s) / (i + 1))
            s += (i + 1) * m
            l += m
    return l <= k


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

ok, ng = 0, 10 ** 15 + 1
while abs(ok - ng) > 1:
    mid = (ok + ng) // 2
    if is_ok(mid):
        ok = mid
    else:
        ng = mid

print(ok)