#include <fstream>
#include <deque>

using namespace std;

ifstream f("deque.in");
ofstream g("deque.out");
int v[5000005];
int n, k;
deque<long long> q;
long long s = 0;

int main()
{
    f>>n>>k;
    for(int i = 1; i<=n; i++)
    {
        f>>v[i];
    }

    for(int 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)
        {
            s += v[q.front()];
        }
    }

    g<<s;

    return 0;
}