#include <fstream>

using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
int s,i,n,q[5000001],v[500001],nr,u,p,k;
int main()
{
    f>>n>>k;

    for(i=1;i<=n;i++)
        f>>v[i];
    q[1]=1;
    u=p=1;
    for(i=2;i<=n;i++){
    while(v[i]<=v[q[u]]&&p<=u)
        u--;
        q[++u]=i;
    while(i-nr>k&&nr<i){
        nr++;
    if(nr==q[p])
        p++;
    }
    if(i-nr==k)
        s+=v[q[p]];
    }
    g<<s;

    return 0;
}