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

N,M=map(int,input().split())
A=list(map(int,input().split()))
def is_ok(ans):
    C=A[:]
    for i in range(N):
        if C[i]<ans:
            return False
        if i<N-1:
            C[i+1]+=C[i]-ans
    return True
ans=Bisect_Int(0,max(A)+1,is_ok)//M
print(ans)