#include <fstream>
#include <deque>
using namespace std;
ifstream cin("deque.in");
ofstream cout("deque.out");
long long s,mn=99999999,i,d,a[5000005],n,k;
int main()
{
    cin>>n>>k;
    for(i=1; i<=n; i++)
    {
        cin>>a[i];
    }
    deque <int>dq;
    for(i=1; i<=n; i++)
    {
        while(!dq.empty()&&a[dq.back()]>=a[i])
        {
            dq.pop_back();
        }
        dq.push_back(i);
        if(dq.front()==i-k)
        {
            dq.pop_front();
        }
        if(i>=k)
        {
            s=s+a[dq.front()];
        }
    }
    cout<<s;
    return 0;
}