#include <fstream>
#include <deque>
using namespace std;

deque<int>d;
int n,i,k,v[5000005];
long long 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",&v[i]);
        while(!d.empty()&&v[d.back()]>=v[i])
        {
            d.pop_back();
        }
        d.push_back(i);
        if(i-d.front()==k)d.pop_front();
        if(i>=k)s=s+v[d.front()];
    }
    printf("%d",s);
    return 0;
}