#include <bits/stdc++.h>

using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int v[5000011], i, n, k;
long long ans;
deque<int> d;
int main()
{
    fin >> n >> k;
    for(i = 1; i <= n; ++ i)
    {
        fin >> v[i];
        while(!d.empty() && v[d.back()] >= v[i])
            d.pop_back();
        d.push_back(i);
        if(i - d.front() == k)
            d.pop_front();
        if(i >= k)
            ans += v[d.front()];
    }
    fout << ans;
    return 0;
}