#include <bits/stdc++.h>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int n, k;
deque<int> dq;
int v[5000005];
int main()
{
    long long sum=0;
    fin >> n >> k;
    for(int i=1; i <= n; i++)
        fin >> v[i];
    for(int i=1; i <= n; i++)
    {
        while(!dq.empty() && v[i] <= v[dq.back()])
            dq.pop_back();
        dq.push_back(i);
        if(!dq.empty() && dq.front()<=i-k)
            dq.pop_front();
        if(i>=k)
            sum+=v[dq.front()];
    }
    fout << sum;
    return 0;
}