#include <bits/stdc++.h>
#define int long long
using namespace std;

const int N = 2e5 + 5;
int n, m, a[N];
bool check(int mid)
{
	int tot = 1;
	for (int i = 1; i <= m; i++)
	{
		int sum = 0;
		while (sum + a[tot] + 1 <= mid)
		{
			sum += a[tot];
			sum++;
			tot++;
		}
		if (sum + a[tot] + 1 == mid + 1)
		{
			sum += a[tot];
			tot++;
		}
		if (tot > n)
		{
			break;
		}
	}
	if (tot > n)
	{
		return 1;
	}
	return 0;
}

signed main()
{
	ios::sync_with_stdio(0);
	cin.tie();cout.tie();
	cin >> n >> m;
	for (int i = 1; i <= n; i++)
	{
		cin >> a[i];
	}
	int l = 1, r = 1e15;
	while (l < r)
	{
		int mid = (l + r) / 2;
		if (check(mid))
		{
			r = mid;
		}
		else
		{
			l = mid + 1;
		}
	}
	cout << r;
	return 0;
}