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

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

deque<int> deq;
long long n, k, v[5000005], s;

int main() {
    f >> n >> k;
    for(int i = 1; i <= n; i++)
        f >> v[i];

    deq.push_back(1);
    for(int i = 2; i <= n; i++) {
        while(v[i] < v[deq.back()])
            deq.pop_back();
        deq.push_back(i);

        if(i >= k) {
            if(deq.front() <= i-k)
                deq.pop_front();
            s += v[deq.front()];
        }
    }

    g << s;
}