#include <fstream>
#include <deque>
using namespace std;
int v[5000005];
int n,k,i;
long long s=0;
ifstream fin("deque.in");
ofstream fout("deque.out");
deque <int> dq;
int main()
{
    fin>>n>>k;
    for (i=1;i<=n;i++) {
        fin>>v[i];
    }
    dq.push_back(1);
    for (i=2;i<=n;i++){
        while (!dq.empty() && v[i]<=v[dq.back()]) {
            dq.pop_back();
        }
        dq.push_back(i);
        if (i-dq.front()==k) {
            dq.pop_front();
        }
        if (i>=k){
            s+=v[dq.front()];
        }
    }
    fout<<s;
    return 0;
}