#include <fstream>
#include <deque>
using namespace std;
ifstream is ("deque.in");
ofstream os ("deque.out");
deque <int> D;
int n, k, a[5000001];
long long S;

int main()
{
    is >> n >> k;
    for(int i = 1; i <= n; ++i)
        is >> a[i];

    for (int i = 1; i <= n; i++)
    {
        while(!D.empty() && a[i] <= a[D.back()])
        D.pop_back();

        D.push_back(i);

        if(D.front() == i-k)
            D.pop_front();

       if(i>= k)
        S += a[D.front()];
    }
    os << S;

    return 0;
}