#include <bits/stdc++.h>

using namespace std;

ifstream fin("deque.in");

ofstream fout("deque.out");

deque<int> d;

long long sum;

int v[5000005], n, k;

int main()
{
  fin>>n>>k; sum=0;

  for(int i=1;i<=n;++i)
  {
      fin>>v[i];
  }

  for(int i=1;i<=n;++i)

    {while(!d.empty() && v[d.back()]>v[i])

       d.pop_back();

      d.push_back(i);


       if(d.front()==i-k) d.pop_front();

       if(i>=k) sum+=v[d.front()];

    }


  fout<<sum;

    return 0;
}