#include<fstream>
using namespace std;
 int v[5000001],d[5000001],i,n,k,p,u;
long long s;
 int main()
{    ifstream f("deque.in");   
 ofstream g("deque.out");
    f >> n >> k;
    for (i=1;i<=n;i++)
        f >> v[i];
    p=1;u=0;s=0;
    for (i=1;i<=n;i++)
    {        while ((p<=u) && (v[i]<=v[d[u]])) u--; 
       u++; d[u]=i; 
       if (i-d[p]==k) p++;
        if (i>=k) s+=v[d[p]];
    } 
   g << s;
}