#include <bits/stdc++.h>

using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int n,i,k,ans,v[5000005];
deque <int> s;
int main()
{
    fin >> n >> k;
    for (i=1; i<=n; i++)
    {
        fin >> v[i];
        while (!s.empty() && v[s.front()]>=v[i])
            s.pop_front();
        s.push_front(i);
        if (s.back()==i-k) s.pop_back();
        if (i>=k) ans+=v[s.back()];
    }
    fout << ans;
    return 0;
}