#include <cstdio>
#include <deque>

#define MaxN 5000005

using namespace std;

int n, k, v[MaxN];
deque<int> q;
long long sum = 0;

int main() {

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

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

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

    for (int i = 1; i <= n; i++) {
        if (!q.empty() && q.front() == i - k)
            q.pop_front();

        while (!q.empty() && v[q.back()] >= v[i])
            q.pop_back();

        q.push_back(i);

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

    printf("%lld", sum);

    return 0;
}