#include <fstream>
#include <deque>

using namespace std;

long long s = 0;
deque<int> d;
int n, k, v[5000010];

void Read()
{
    ifstream fin("deque.in");
    fin >> n >> k;
    for (int i = 1;i <= n;++i)
        fin >> v[i];
    fin.close();
}

void Solve()
{
    for (int 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)
            s += v[d.front()];
    }
}

void Write()
{
    ofstream fout("deque.out");
    fout << s << "\n";
    fout.close();
}

int main()
{
    Read();
    Solve();
    Write();
    return 0;
}