#include <cstdio>
#include <deque>
#include <vector>

using namespace std;

int main()
{
  freopen("deque.in", "r", stdin);
  freopen("deque.out", "w", stdout);

  deque<int> deq;
  vector<int> v;  
  int N, K;
  long long total = 0;
  
  scanf("%d%d", &N, &K);
  v.resize(N);

  for (int i = 0; i < N; ++i) {
    scanf("%d", &v[i]);
    while (!deq.empty() && v[deq.back()] >= v[i])
      deq.pop_back();
    deq.emplace_back(i);
    while (!deq.empty() && i - deq.front() >= K)
      deq.pop_front();

    if (i >= K - 1)
      total += 1LL*v[deq.front()];    
  }

  printf("%lld", total);
  
  return 0;
}