def General_Binary_Decrease_Search_Integer(L, R, cond, default=None):
    """ 条件式が単調減少であるとき, 整数上で二部探索を行う.

    L: 解の下限
    R: 解の上限
    cond: 条件 (1変数関数, 広義単調減少 を満たす)
    default: R で条件を満たさないときの返り値
    """

    if not(cond(L)):
        return default

    if cond(R):
        return R

    L-=1
    while R-L>1:
        C=L+(R-L)//2
        if cond(C):
            L=C
        else:
            R=C
    return L

#==================================================
import heapq

class Double_Heap:
    def __init__(self):
        self.__small=[]
        self.__large=[]
        self.__dict={}
        self.__length=0
        self.__sum=0

    def __bool__(self):
        return bool(self.__length)

    def __len__(self):
        return self.__length

    def __contains__(self, x):
        return self.is_exist(x)

    def push(self, x):
        self.__length+=1
        self.__sum+=x

        heapq.heappush(self.__small, x)
        heapq.heappush(self.__large, -x)

        if x in self.__dict:
            self.__dict[x]+=1
        else:
            self.__dict[x]=1

    def discard(self, x):
        """ x を消す (存在しない場合は何もしない). """

        if x not in self:
            return

        self.__dict[x]-=1
        if self.__dict[x]==0:
            del self.__dict[x]

        self.__length-=1
        self.__sum-=x

        while self.__small and (self.__small[0] not in self):
                heapq.heappop(self.__small)

        while self.__large and (-self.__large[0] not in self):
                heapq.heappop(self.__large)

    def is_exist(self, x):
        """ キューに x が存在するかどうかを判定する. """
        return x in self.__dict

    def get_min(self):
        assert self
        return self.__small[0]

    def pop_min(self):
        assert self
        x=self.get_min()
        self.discard(x)
        return x

    def get_max(self):
        assert self
        return -self.__large[0]

    def pop_max(self):
        assert self
        x=self.get_max()
        self.discard(x)
        return x

    def count(self, x):
        """ x の個数を求める. """

        return self.__dict.get(x,0)

    def sum(self):
        return self.__sum

    def __str__(self):
        return str(self.__dict)

    def __repr__(self):
        return "[Double Heap]: "+str(self)

#==================================================
def solve():
    N,K=map(int,input().split())
    A=[-1]+list(map(int,input().split()))

    def check(X):
        count=0
        added=0
        for i in range(1,N+1):
            delta=max(0, X-(A[i]+added))
            k=(delta+i-1)//i
            count+=k
            added+=i*k
        return count<=K

    return General_Binary_Decrease_Search_Integer(0,10**15,check,-1)
#==================================================
print(solve())