#include <bits/stdc++.h>

using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
long long n, k, v[5000010], sum = 0;
deque<int> dq;

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

    return 0;
}