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