def is_ok(V):
    cnt = 0
    add = 0
    for i,a in enumerate(A,start=1):
        if add+a<V:
            temp = -(-(V-a-add)//i)
            add+=temp*i
            cnt+=temp
    return cnt<=K

def meguru_bisect(ng, ok):
    while (abs(ok - ng) > 1):
        mid = (ok + ng) // 2
        if is_ok(mid):
            ok = mid
        else:
            ng = mid
    return ok




N,K = map(int, input().split())
A = list(map(int, input().split())) 

print(meguru_bisect(10**18,0))