#include <fstream>
#include <deque>

FILE *fin = freopen("deque.in","r",stdin);
FILE *fout = freopen("deque.out","w",stdout);

static const int NMAX = 5e6 + 5;
/* -------- DATA ---------- */
int n, k,v[NMAX];
std::deque<int> deq;
/* -------- DATA ---------- */

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

    long long sum =0;
    for(int i = 1; i<= n; ++i)
    {
        while(!deq.empty() && v[i] <= v[deq.back()])
            deq.pop_back();
        deq.push_back(i);
        if(!deq.empty() && i - deq.front() == k)
            deq.pop_front();
        if(i>=k)
            sum+= v[deq.front()];
    }
    printf("%lld",sum);

    return 0;
}