#include <cstdio>
#include <deque>
#define Nmax 5000010
using namespace std;
deque < int > deq;
long long suma;
int vec[Nmax];
int n,k;
void read()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    scanf("%d %d",&n,&k);
    int x;
    deq.push_front(1);
    vec[1] = 10000000;
    for(int i = 2 ; i <= n ; i++)
    {
        scanf("%d ",&vec[i]);
        int x = deq.back();
        int y = deq.front();
        while(!deq.empty() && vec[x] >= vec[i])
            deq.pop_back();
        deq.push_back(i);
         x = deq.back();
        if( y <= i - k)
        {
            deq.pop_front();
             y = deq.front();
        }
        if(i >= k)
            suma += vec[y];

    }
}

int main()
{
    read();
    printf("%d",suma);
    return 0;
}