#include <cstdio>
#include <deque>
using namespace std;
deque <int> b;
int a[5000001],n,k;
long long 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("%d",&a[i]);
    for(int i=1;i<=n;i++)
    {
        while(!b.empty() && a[i]<a[b.back()])
                b.pop_back();
        b.push_back(i);
        if(b.front()<=i-k)
            b.pop_front();
        if(i>=k)
            s+=a[b.front()];
    }
    printf("%d\n",s);
    return 0;
}