#include <cstdio>
#include <deque>
#define jos -10000001
using namespace std;
deque <int> v;
long long s=0,val[5000009];
int main()
{
    int n,k,i;
    int a;
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    val[0]=jos;
    v.push_back(0);
    scanf("%d%d",&n,&k);
    for(i=1;i<=n;i++)
    {
          scanf("%d",&a);
          val[i]=a;
          while(a<=val[v.back()]&&!v.empty())
          {
                v.pop_back();
          }
          v.push_back(i);
          while(v.front()<=i-k)
          {
                v.pop_front();
          }
          if(i>=k)
           {
             s=s+val[v.front()];
           }

    }
    printf("%lld\n",s);
    return 0;
}