#include <fstream>
#include <deque>

using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
int a[5000005];
deque <long long> dq;

int main()
{
    int n,k,i;
    long long sum=0;
    f>>n>>k;
    for(i = 1 ; i <= n; ++i)
        f>>a[i];
    for(i = 1 ; i <= n; ++i)
    {
        while(!dq.empty() && a[i]<= a[dq.back()])
            dq.pop_back();
        dq.push_back(i);
        if(i-k == dq.front())
            dq.pop_front();
        if(i >= k)
            sum += a[dq.front()];
    }
    g<<sum;
}