#include <fstream>
#include <deque>
using namespace std;
int v[5000001];
ifstream in("deque.in");
ofstream out("deque.out");
int main()
{
    deque <int> q;
    int n, k, x;
    long long r=0;
    in>>n>>k;
    for(int i=1; i<=n; i++)
    {
        in>>v[i];
        if(!q.empty() && i-q.front()==k)
        {
            q.pop_front();
        }
        while(!q.empty() && v[i]<=v[q.back()])
        {
            q.pop_back();
        }
        q.push_back(i);
        if(i>=k)
        {
            r+=v[q.front()];
        }
    }
    out<<r;
}