#include <cstdio>
#include <deque>

using namespace std;

deque <long long>q;
int n, k;
long long a[5000005], 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("%lld", &a[i]);
    for(int i=1;i<=n;i++)
    {
        while(!q.empty() && a[i]<=a[q.back()])
            q.pop_back();
        q.push_back(i);
        while(!q.empty() && q.front()<=i-k)
            q.pop_front();
        if(i>=k)
            s+=a[q.front()];
    }
    printf("%lld", s);

    return 0;
}