#include <fstream>
#include <set>
using namespace std;
ifstream fi("deque.in");
ofstream fo("deque.out");
multiset < int > ms;
multiset<int>::iterator it;
int n,i,j,k,s,x,y,a[5000001];
long long mini;

int main()
{
   fi>>n>>k;
   for(i=1;i<=n;i++)fi>>a[i];
   for(i=1;i<=n;i++){
      ms.insert(a[i]);
      if(i>=k) {
                it=ms.begin();
                mini+=*it;
                ms.erase(a[i-k+1]);
       }
   }
  fo<<mini;
  return 0;
}