#include <fstream>
#include <deque>

using namespace std;


ifstream fin("deque.in");
ofstream fout("deque.out");
const int Nmax = 1e6 * 5 + 5;
int v[Nmax];
long long ans;
deque <long long> A;


signed main()
{
    int n, k, i;

    fin >> n >> k;
    for(i = 1; i <= n; i++)
        fin >> v[i];

    for(i = 1; i <= n; i++)
    {
        while(!A.empty() && v[A.back()] >= v[i])
            A.pop_back();
        A.push_back(i);

        if(A.front() == i - k)
            A.pop_front();
        if(i >= k)
            ans += v[A.front()];
    }
    fout << ans;

    return 0;
}