#include <iostream>
#include <deque>

using namespace std;

int main() {
    int n, k;
    cin >> n >> k;
    int a[n] = {0};
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }
    int max = -1;
    while (k) {
        int sum = 0;
        for (int i = 0; i < k; i++) {
            sum += a[i];
        }
        if (max < sum) max = sum;
        for (int i = k; i < n; i++) {
            sum += a[i];
            sum -= a[i - k];
            if (max < sum) max = sum;
        }
        k--;
    }
    cout << max;
    return 0;
}

status:{ [ "1", "1", "1", "0", "0", "1", "1", "1", ] }

lol:)