#include <fstream>
#include <queue>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");

int N, a[5000005], K;
long long sol;
deque < int > Q;

int main()
{
    f>>N>>K;
    for (int i=1; i<=N; ++i)
    {
        f>>a[i];
        while (Q.size() && a[Q.back()]>=a[i]) Q.pop_back();
        Q.push_back(i);

        if (i-Q.front()>=K) Q.pop_front();
        if (i>=K)
            sol+=1LL*a[Q.front()];
    }

    g<<sol<<'\n';
    return 0;
}