#include <algorithm>
#include <cstdio>
#include <deque>

const int maxN = 5e6;
std :: deque<int> D;
int v[maxN + 1], N, K;
long long ans;

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

  scanf("%d %d", &N, &K);
  for(register int i = 1; i <= N; ++ i) {
    scanf("%d", &v[i]);
    while(!D.empty() and v[i] <= v[D.back()])
      D.pop_back();
    D.push_back(i);
    if(D.front() == i - K)
      D.pop_front();
    if(i >= K)
      ans += v[D.front()];
  }
  printf("%lld\n", ans);
  return 0;
}