#include <bits/stdc++.h>

using namespace std;

const int N = 100010;
typedef long long ll;
int a[N];
ll s[N], f[N];

/*
BruteForce
通过了 9/12个数据
*/
int main() {
    int n, m;
    cin >> n >> m;
    for (int i = 1; i <= n; i++) cin >> s[i], s[i] += s[i - 1];

    // 暴力大法
    for (int i = 1; i <= n; i++)
        for (int j = i; j >= i - m; j--)
            f[i] = max(f[i], f[j - 1] + s[i] - s[j]);

    cout << f[n] << endl;
    return 0;
}