#include <bits/stdc++.h>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int n,k,v[5000010];
long long ans;
deque <int> dq;
int main()
{
    fin>>n>>k;
    for(int i=1;i<=n;i++)
        fin>>v[i];
    dq.push_front(1);
    for(int i=1;i<=n;i++)
    {
        while(dq.front()<=dq.back()&&v[i]<=v[dq.back()])
            dq.pop_back();
        dq.push_back(i);
        if(dq.front()==i-k)
            dq.pop_front();
        if(i>=k)
            ans+=v[dq.front()];
    }
    fout<<ans;
    return 0;
}