#include <fstream>
#include <deque>
#define NMAX  5000000
using namespace std;
ifstream fin ("deque.in");
ofstream fout ("deque.out");

int n, k, x;
int v[NMAX+2];
long long s;
deque <int> d;
int main()
{
    fin>>n>>k;
    for(int i=1; i<=n; i++)
        fin>>v[i];
    for(int i=1; i<=n; i++)
    {
        ///minimul unei secv care se termina pe poz i si care e de lungime k
        while(!d.empty() && v[i]<=v[d.back()])
            d.pop_back();
        d.push_back(i);
        if(i-d.front()==k)
            d.pop_front();
        if(i>=k)
            s+=v[d.front()];

    }
   fout<<s;




    return 0;
}