import sys
import bisect

def main():
    N, K = map(int, sys.stdin.readline().split())
    A = list(map(int, sys.stdin.readline().split()))
    sum_A = sum(A)
    if K == 0:
        print(0)
        return
    if sum_A < K:
        print(0)
        return

    low = 0
    high = sum_A // K  # 初始猜测，可以更高
    ans = 0

    while low <= high:
        mid = (low + high) // 2
        # 复制数组
        B = A + A
        # 计算前缀和
        pre_sum = [0] * (2 * N + 1)
        for i in range(1, 2*N+1):
            pre_sum[i] = pre_sum[i-1] + B[i-1]
        # 预处理next数组
        next_j = [2*N] * (2*N + 1)
        for i in range(2*N + 1):
            target = pre_sum[i] + mid
            # 在[i+1, 2N]中找最小j，使得pre_sum[j] >= target
            j = bisect.bisect_left(pre_sum, target, i+1, 2*N +1)
            if j <= 2*N:
                next_j[i] = j
            else:
                next_j[i] = 2*N + 1  # 表示无法分割
        # 检查每个窗口
        found = False
        for i in range(N):
            current = i
            cnt = 0
            while current <= i + N -1:
                j = next_j[current]
                if j > i + N:
                    break
                cnt += 1
                if cnt >= K:
                    found = True
                    break
                current = j
            if found:
                break
        if found:
            ans = mid
            low = mid + 1
        else:
            high = mid -1
    print(ans)

if __name__ == '__main__':
    main()