#include <bits/stdc++.h>

using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
deque<int>Q;
int v[5000010];
int main()
{
    int n,k;
    long long sum=0;
    fin>>n>>k;
    for(int i=1;i<=n;i++)
    {
        fin>>v[i];
        while(Q.size() && i-Q.front()>=k) Q.pop_front();
        while(Q.size() && v[i]<=v[Q.back()]) Q.pop_back();
        Q.push_back(i);
        if(i>=k)
        {
            sum+=v[Q.front()];
        }
    }
    fout<<sum;
}