#include <cstdio>
#include <deque>

using namespace std;

deque <int> d;

int n, k, sum, x;
int a[5000010];

int main()
{

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

    scanf("%d %d", &n, &k);
    int i;
    for(i=1; i<=n; i++)
    {
        scanf("%d", &a[i]);
        while(!d.empty() && a[i]<=a[d.back()])
            d.pop_back();
        d.push_back(i);
        while(!d.empty() && d.front() <= i-k)
            d.pop_front();
        if(i>=k)
            sum+=a[d.front()];

    }
    printf("%d", sum);
    return 0;
}