package main

import (
	"bufio"
	"fmt"
	"os"
)

func main() {
	in := bufio.NewReader(os.Stdin)
	out := bufio.NewWriter(os.Stdout)
	defer out.Flush()

	var n, k int
	fmt.Fscan(in, &n, &k)
	nums := make([]int, n)
	for i := 0; i < n; i++ {
		fmt.Fscan(in, &nums[i])
	}

	presum := make([]int, n+1)
	for i := 0; i < n; i++ {
		presum[i+1] = presum[i] + nums[i]
	}

	check := func(mid int) bool {
		count := make([]int, n)
		leftMost := make([]int, n)
		for i := 0; i < n; i++ {
			count[i] = 1
			leftMost[i] = i
		}
		left := -1
		for right := 0; right < n; right++ {
			for left+1 < right && presum[right]-presum[left+1] >= mid {
				left++
			}
			if left >= 0 {
				count[right] = count[left] + 1
				leftMost[right] = leftMost[left]
				if count[right] == k {
					// 首尾
					if presum[n]-(presum[right]-presum[leftMost[right]]) >= mid {
						return true
					}
				}
			}
		}
		return false
	}

	sum := 0
	for i := 0; i < n; i++ {
		sum += nums[i]
	}
	left, right := 1, sum/k+1
	for left <= right {
		mid := (left + right) / 2
		if check(mid) {
			left = mid + 1
		} else {
			right = mid - 1
		}
	}

	fmt.Fprintln(out, right)
}