#include <cstdio>
#include <queue>

using namespace std;

deque<int> q;
int v[5000002];

int main()
{
    freopen("deque.in", "r", stdin);
    freopen("deque.out", "w", stdout);

    int n, k;
    scanf("%d%d", &n, &k);

    for (int i = 1; i <= n; i++)
        scanf("%d", &v[i]);

    long long sol = 0;
    for (int i = 1; i <= n; i++)
    {
        while (!q.empty() && v[i] <= v[q.back()])
            q.pop_back();
        q.push_back(i);

        if (q.front() <= i-k)
            q.pop_front();

        if (i >= k)
            sol += v[q.front()];
    }

    printf("%lld\n", sol);

    return 0;
}