#include <bits/stdc++.h>
#include <deque>
#include <fstream>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int main() {
  long long n, k, ans = 0;
  fin >> n >> k;
  deque<long long> dq;
  map<long long, long long> mp;
  for (int i = 0; i < n; i++) {
    long long x;
    fin >> x;
    dq.push_back(x);
    mp[x]++;
    if (dq.size() > k) {
      mp[dq.front()]--;
      if (mp[dq.front()] == 0)
        mp.erase(dq.front());
      dq.pop_front();
    }
    if (dq.size() == k)
      ans += mp.begin()->first;
  }
  fout << ans;
  return 0;
}