class Fenwick_Tree:
    def __init__(self, n):
        self._n = n
        self.data = [0] * n

    def add(self, p, x):
        assert 0 <= p < self._n
        p += 1
        while p <= self._n:
            self.data[p - 1] += x
            p += p & -p

    def sum(self, l, r):
        assert 0 <= l <= r <= self._n
        return self._sum(r) - self._sum(l)

    def _sum(self, r):
        s = 0
        while r > 0:
            s += self.data[r - 1]
            r -= r & -r
        return s
    
    def get(self, k):
        k += 1
        x, r = 0, 1
        while r < self._n:
            r <<= 1
        len = r
        while len:
            if x + len - 1 < self._n:
                if self.data[x + len - 1] < k:
                    k -= self.data[x + len - 1]
                    x += len
            len >>= 1
        return x

def check(m):
    T = Fenwick_Tree(N)
    cnt = 0
    for i in range(N):
        if A[i] >= m:
            continue
        s = T.sum(0, i + 1)
        v = max(0, (m - A[i] - s + i)//(i + 1))
        cnt += v 
        T.add(i, v * (i + 1))
    return cnt <= K

N, K = map(int, input().split())
A = list(map(int, input().split()))
yes = 0
no = 10 ** 15
while no - yes != 1:
    mid = (yes + no)//2
    if check(mid):
        yes = mid
    else:
        no = mid
print(yes)