#include<cstdio>
#include<deque>

using namespace std;

deque<int>dq;
int i,k,n,a[5000002],s;

int main()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    scanf("%d%d",&n,&k);
    for(i=1;i<=n;i++)
    {
        scanf("%d",&a[i]);
        if(i<=k)
        {
            while(!dq.empty()&&a[dq.back()]>=a[i])
            {
                dq.pop_back();
            }
            dq.push_back(i);
        }
    }
    s+=a[dq.front()];
    for(i=k+1;i<=n;i++)
    {
        while(!dq.empty()&&dq.front()<=i-k)
        {
            dq.pop_front();
        }
        while(!dq.empty()&&a[dq.back()]>=a[i])
        {
            dq.pop_back();
        }
        dq.push_back(i);
        s+=a[dq.front()];
    }
    printf("%d\n",s);
    return 0;
}