#include <fstream>
#include <deque>
using namespace std;

int n, k;
deque < pair<int, int> > d;
long long s;

int main() 
{
    ifstream fin("deque.in");
    ofstream fout("deque.out");
     fin >> n >>k;
     for(int i=0; i<n; ++i)
     {
             int v;
             fin>>v;
             while(!d.empty()&& d.back().first>v)
             d.pop_back();
             
             d.push_back(make_pair(v, i));
             if (d.front().second + k==i);
             d.pop_front();
             s+= i< k - 1 ? 0 : d.front().first;
             }
             fout<<s;
             }