#include <fstream>
#include <deque>

#define nMax 5000007

using namespace std;

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

deque<int> q;
int v[nMax];
int n, k;
long long s;

int main()
{
    in >> n >> k;
    for(int i = 1; i <= n; ++i)
        in >> 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()];
    }
    out << s;
    return 0;
}