#include <bits/stdc++.h>

using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int n,k,a[5000005],i,s;
deque<int> m;
int main()
{
    fin>>n>>k;
    for(i=1;i<=n;i++)
    {
        fin>>a[i];
    }
    m.push_back(1);
    for(i=2;i<=k;i++)
    {
        while(!m.empty()&&a[i]<=a[m.back()])m.pop_back();
        m.push_back(i);
    }
    s+=a[m.front()];
    for(i=k+1;i<=n;i++)
    {
        while(!m.empty()&&m.front()+k<=i)m.pop_front();
        while(!m.empty()&&a[i]<=a[m.back()])m.pop_back();
        m.push_back(i);
        s+=a[m.front()];
    }
    fout<<s;
    return 0;
}