#include <iostream>
#include <fstream>
#include <deque>
using namespace std;

deque <int> d;

int n, k, v[5000002], s;

int main()
{
    ifstream fin ("deque.in");
    ofstream fout ("deque.out");
    fin >> n >> k;
    for(int i = 1; i <= n; i++)
        fin >> v[i];
    for(int i = 1; i <= n; i++)
    {
        if(!d.empty())
        {
            while(!d.empty() && v[d.back()] >= v[i])
                d.pop_back();
            if(!d.empty() && d.front() <= i - k)
                d.pop_front();
        }
        d.push_back(i);
        if(i >= k)
            s += v[d.front()];
    }
    fout << s << "\n";
    return 0;
}