#include<algorithm>
using namespace std;
#include<vector>

#define DIM 5000005

vector <int> d;
int a[DIM],n,k;
long long sol;

int main ()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    int i,j;

    scanf("%d%d",&n,&k);
    for(i=1;i<=n;++i)
    {
        scanf("%d",&a[i]);
        while(!d.empty () && a[i]<=a[d[d.size()-1]])
            d.pop_back ();
        d.push_back (i);

        while(!d.empty () && d[0]<=i-k)
            d.erase (d.begin ());
        if(i>=k)
            sol+=a[d[0]];
    }
    printf("%lld",sol);
    return 0;
}