#include <iostream>
#include <fstream>
#include <queue>

using namespace std;

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

int n, k, x, s;
int v[5000001];
deque<int> dq;

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