#include <fstream>
#include <deque>
using namespace std;
ifstream in("deque.in");
ofstream out("deque.out");
int n, k, v[5000001];
int main()
{   in >> n >> k;
    for(int i = 1; i <= n; ++i) in >> v[i];
    deque<int> d;
    long long s = 0;
    for(int i = 1; i <= n; ++i)
    {   while(!d.empty() && v[d.front()] >= v[i]) d.pop_front();
        d.push_front(i);
        if(d.back() <= i - k) d.pop_back();
        if(i >= k)  s += v[d.back()];
    }
    out << s;
    return 0;
}