#include<fstream>
#include<deque>
using namespace std;
ifstream cin("deque.in");
ofstream cout("deque.out");
int main()
{
    long long n,k,s=0,val;
    int nr=0,v[500001];
    deque<int> d;
    cin>>n>>k;
    for(int i=1; i<=n; i++)
        cin>>v[i];
    for(int i=1; i<=n; i++)
    {
        while(d.empty()==0 && v[i]<v[d.back()])
            d.pop_back();
        d.push_back(i);
        if(d.front()==i-k)
            d.pop_front();
        if(i>=k)
            s+=v[d.front()];
    }
    cout<<s;
    return 0;
}