#include <fstream>
#include <deque>
#include <vector>
std::ifstream in("deque.in");
std::ofstream out("deque.out");

int main()
{
    int n, k, x;
    long long s = 0;
    in>>n>>k;
    std::deque<int> d;
    std::vector<int> v;
    v.reserve(n);
    for (int i = 0; i < n; ++i) {
        in>>x;
        v.push_back(x);
        while (!d.empty() && v[d.back()] >= x)
            d.pop_back();
        d.push_back(i);
        if (d.front() + k == i)
            d.pop_front();
        if (i >= k - 1)
            s += v[d.front()];
    }
    out<<s;
}