#include<cstdio>
#include<deque>
using namespace std;
deque<int> coada;
int i, n, a[5000001], k;
long long suma;
int main()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    scanf("%d %d\n", &n, &k);
    suma=0;
    for (i=1; i<=n; i++) scanf("%d\n", &a[i]);
    for (i=1; i<=n; i++) {
        while ((!coada.empty())&&(a[i]<a[coada.back()])) coada.pop_back();
        coada.push_back(i);
        if (coada.front()<=i-k) coada.pop_front();
        if (i>=k) suma+=a[coada.front()];
    }
    printf("%lld", suma);
    return 0;
}