#include <fstream>
#include <deque>

using namespace std;

ifstream in("deque.in");
ofstream out("deque.out");

const int N=5e6+2;

deque <int> dq;

long long v[N];

int main()
{
    int n,k;
    long long ans=0;
    in>>n>>k;
    for(int i=1;i<=n;++i)
    {
        in>>v[i];
        while(!dq.empty() && dq.front()==i-k)
        {
            dq.pop_front();
        }
        while(!dq.empty() && v[dq.back()]>=v[i])
        {
            dq.pop_back();
        }
        dq.push_back(i);
        if(i>=k)
        {
            ans+=v[dq.front()];
        }
    }
    out<<ans;
    return 0;
}