#include <fstream>
#include <deque>
#define NMAX 5000005

using namespace std;

const char inname[] = "deque.in";
const char outname[] = "deque.out";
ifstream fin(inname);
ofstream fout(outname);

deque <int> D;
int n, k, v[NMAX];
long long int suma;

void citire();
void rez();

int main(){
    citire();
    rez();
    fout << suma << '\n';
    fin.close();
    fout.close();
    return 0;
}

void citire(){
    int i;
    fin >> n >> k;
    for(i=1; i<=n; i++)
        fin >> v[i];
}

void rez(){
    int i;
    for(i=1; i<=n; i++){
        while(!D.empty() && v[D.back()]>=v[i])
            D.pop_back();
        D.push_back(i);
        if(i-k == D.front())
            D.pop_front();
        if(i >= k)
            suma += v[D.front()];
        }
}