#include <fstream>
#include <deque>
#define N 5000010
#define intt long long
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
intt n, v[N], k, ans;
deque <intt> Q;

int main()
{
    f >> n >> k;
    for(intt i = 1; i <= n; ++i)
        f >> v[i];
    for(intt i = 1; i <= n ; ++i )
    {
        while(!Q.empty() && v[i] <= v[Q.back()] ) Q.pop_back();
        Q.push_back(i);
        if(Q.front() == i-k) Q.pop_front();
        if(i >= k)
            ans += v[Q.front()];
    }
    g << ans;
    f.close(); g.close();
    return 0;
}