#include<fstream>
#include<iostream>
using namespace std;

int a[500000],i,k, n;

int min(int p)
{ int min=a[p],i;
    for(i=p+1;i<=p+k;i++)
     if(a[i]<min)
       min=a[i];
    
  return min;
}

int main()
{int s;
    ifstream f("deque.in");
       f>>n>>k;
     for(i=1;i<=n;i++)
       f>>a[i];
     f.close();
     
    for(i=1;i<=n;i++)
      s=s+min(i);
     
ofstream g("deque.out");
   g<<s;
   g.close();
       return 0;
       }