#include <fstream>
#define maxn 5000010

using namespace std;

ifstream fin("deque.in");
ofstream fout("deque.out");
int n,k,i,p,u;
long long sum;
int a[maxn],deq[maxn];
int main()
{
   fin>>n>>k;
   for(i=1;i<=n;i++)
    fin>>a[i];
    p=1;
    u=0;
   for(i=1;i<=n;i++)
   {
       while(p<=u && a[i]<a[deq[u]]) u--;
       deq[++u]=i;
       if(i-deq[p]>=k)
        p++;
       if(i>=k)
        sum+=a[deq[p]];
   }
    fout<<sum;
    return 0;
}