#include<fstream>
#include<deque>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int v[5000002];
deque <int>d;
long long s;
int main()
{
    int n,k,i;
    //citire
    fin>>n>>k;
    for(i=1; i<=n; i++)
        fin>>v[i];



    for(i=1; i<=n; i++)
    {
        while(!d.empty()&&v[d.back()]>=v[i])
            d.pop_back();
        d.push_back(i);
        if(d.front()==i-k)
            d.pop_front();
        if(i>=k)
            s+=v[d.front()];
    }
    fout<<s;
}