#include <fstream>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
int n,k,s,d[5000010],v[5000010],i,u,p;
int main()

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


    }
    g<<s;
}