#include<iostream>
#include <fstream>
#include<string>
#include<vector>

using namespace std;


int main() {
	freopen("krasi.in", "r", stdin);
	freopen("krasi.out", "w", stdout);
	int n = 0;
	cin >> n;
	int k = 0;
	cin >> k;
	int* nums = new int[n];
	for (int i = 0; i < n; i++) {
		cin >> nums[i];
	}
	int max_so_far = -1001; 
	int max_ending_here = 0;
	int zeros = 0;
	int rem = 0;
	for (int i = 0; i < n; i++)
	{
		max_ending_here = max_ending_here + nums[i];
		if (nums[i] == 0) {
			zeros++;
			if (zeros == 1) {
				rem = i;
			}
		}
		if (max_so_far < max_ending_here && zeros <= k) {
			max_so_far = max_ending_here;
		}
		
		if (max_ending_here < 0 || zeros > k) {
			max_ending_here = 0;
			zeros = 0;
			i = rem + 1;
		}
	}
	cout<<max_so_far;

	return 0;
}