#include <fstream>
#include <vector>
#include <deque>
using namespace std;
ifstream cin("deque.in");
ofstream cout("deque.out");
int n, k;
long long s;
vector <int> v;
deque <int> dq;
int main()
{
    cin >> n >> k;
    v.resize(n + 2);
    for(int i=1; i<=n; i++)
        cin >> v[i];
    for(int i=1; i<=n; i++)
    {
        while(!dq.empty() && v[dq.front()] >= v[i])
            dq.pop_front();

        dq.push_front(i);

        if(dq.back() <= i - k)
            dq.pop_back();

        if(i >= k)
            s += v[dq.back()];
    }
    cout << s;
    return 0;
}