#include <fstream>
#include <queue>
#define ll long long
using namespace std;
ifstream fi("deque.in");
ofstream fo("deque.out");

deque <int> D;
int n,k;
int A[5000005];

int main()
{
    fi>>n>>k;
    ll sum=0;

    for (int i=1; i<=n; i++)
        fi>>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)
            sum+=A[D.front()];
    }

    fo<<sum;
    return 0;
}