#include <cstdio>
#include <deque>

using namespace std;

int n,k,i,v[5000001];
long long suma;
deque <int> d;

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

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

    for(i=1; i<=n; i++)
    {
        while(!d.empty() && v[d.back()]>=v[i])
            d.pop_back();

        d.push_back(i);

        if(d.front()==i-k) d.pop_front();

        if(i>=k) suma+=v[d.front()];
    }

    printf("%lld",suma);
}