#include <iostream>
#include <stack>
#include <fstream>
#include <deque>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int n, k, v[5000005], k0,cnt,a,ps;
char c;
deque <int> dq;
long long s;
int main()
{
    fin>>n>>k;
    for(int i=1;i<=n;i++)
    {
        fin>>v[i];
    }
    dq.push_back(1);
    for(int i=2;i<=n;i++)
    {
        while(!dq.empty() && v[i]<=v[dq.back()])
        {
            dq.pop_back();
        }
        dq.push_back(i);
        if(i-dq.front()==k)
        {
            dq.pop_front();
        }
        if(i>=k)
        {
            s=s+v[dq.front()];
        }
    }
    fout<<s;
    fin.close();
    fout.close();
    return 0;
}