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

deque <int> Q;
ifstream fin ("deque.in");
ofstream fout ("deque.out");
int main () {
    int n, k, i;
    long long sum=0;
    fin >> n >> k;
    int *v=new int[n+1];
    for (i=1; i<=n; i++)
        fin >> v[i];
    for (i=1; i<=n; i++) {
        while (!Q.empty() && v[i]<=v[Q.back()])
            Q.pop_back();
        Q.push_back(i);
        if (Q.front()==i-k)
            Q.pop_front();
        if (i>=k) sum+=v[Q.front()];
    }
    fout << sum;
    return 0;
}