#include<fstream>
#include<deque>
using namespace std;
deque<int> a;
int n,x,k,i,sol;
int main()
{
    ifstream fin("deque.in");
    ofstream fout("deque.out");
    fin>>n>>k;
    for(i=1;i<=n;i++)
    {
        fin>>x;
        if(a.size()==k) a.pop_back();
        if(a.size()>1)
        while(a.back()>x&&(a.size()>0))
            a.pop_back();
        a.push_front(x);
        if(i>=k)
        sol+=a.back();
    }
    fout<<sol;
    return 0;
}