#include <bits/stdc++.h>
using namespace std;

const int MAXN = 5000005;

ifstream fin("deque.in");
ofstream fout("deque.out");

int n, k, A[MAXN];
deque <int> DQ;
long long sum;

int main()
{
    fin >> n >> k;
    for (int i = 1; i <= n; ++i)
        fin >> A[i];
    for (int i = 1; i <= n; ++i)
    {
        while (!DQ.empty() && A[i] <= A[DQ.back()])
            DQ.pop_back();
        DQ.push_back(i);
        if (DQ.front() == i - k)
            DQ.pop_front();
        if (i >= k) sum += A[DQ.front()];
    }
    fout << sum;
    fin.close();
    fout.close();
    return 0;
}