#include<cstdio>
#include<deque>
using namespace std;
deque<int> deck;
int v[5000007],n,k;
long long s;
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++)
    {
        while(!deck.empty() && v[i]<=v[deck.back()])
            deck.pop_back();
        deck.push_back(i);
        if(deck.front()<=i-k)
            deck.pop_front();
        if(i>=k)
            s+=v[deck.front()];
    }
    printf("%lld",s);
}