#include <fstream>
#include <deque>
using namespace std;

ifstream cin("deque.in");
ofstream cout("deque.out");
const int N = 5000000;
int v[N + 1];
int main()
{
    int n, k, i;
    long long cnt = 0;
    cin >> n >> k;
    deque<int> dq;
    for(i = 1; i <= n; i++)
    {
        cin >> v[i];
    }
    for(i = 1; i <= n; i++)
    {
        while(!dq.empty() && v[dq.back()] >= v[i])
        {
            dq.pop_back();
        }
        dq.push_back(i);
        if(dq.front() <= i - k)
        {
            dq.pop_front();
        }
        if(i >= k)
            cnt += v[dq.front()];
    }
    cout << cnt;
    return 0;
}