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

ifstream cin("deque.in");
ofstream cout("deque.out");


deque<int> q;
int v[500001];
long long s;
int main(){
    int n, k;cin >> n >> k;
    for (int i= 1; i <= n;++i)
    cin >> v[i];
    q.push_back(1);
    for (int i = 2; i <= n;++i){
        while (!q.empty() && v[i] <= v[q.back()])
            q.pop_back();
        q.push_back(i);
        if (i-q.front() == k)
            q.pop_front();
        if (i >=k)
        s+= v[q.front()];
    }
    cout <<s;
}