#include <bits/stdc++.h>

using namespace std;

ifstream f("deque.in");
ofstream g("deque.out");

const int MAX_N = 5'000'000;

int a[MAX_N + 1];
deque<int> d;
long long s;
int n, k;

int main()
{
   f >> n >> k;
   for (int i = 1; i <= n; i++)
      f >> a[i];

   /// Daca i este fixat, atunci i-k+1, ..., i
   /// Pozitia i-k este eliminata din std::deque

   s = 0;
   for (int i = 1; i <= n; i++)
   {
      if (!d.empty() && d.front() == i - k)
         d.pop_front();

      while (!d.empty() && a[i] <= a[d.back()])
         d.pop_back();
      d.push_back(i);

      if (i >= k)
         s += a[d.front()];
   }

   g << s << "\n";

   f.close();
   g.close();
   return 0;
}