#include <iostream>
#include <fstream>
#include <deque>

using namespace std;

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

int n,k,v[5000010];
long long sum;
deque < int > dq;

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