#include<fstream>
#include<deque>
using namespace std;
deque<int> a;
int n,x,k,i,v[5000001];
long long sol;
int main()
{
    ifstream fin("deque.in");
    ofstream fout("deque.out");
    fin>>n>>k;
    for(i=1;i<=n;i++)
    {
        fin>>v[i];
    }
    for(i=1;i<=n;i++)
    {
        if(!a.empty()&&a.front()==i-k)
            a.pop_front();
        while(!a.empty()&&v[a.back()]>v[i])
            a.pop_back();
        a.push_back(i);
        if(i>=k) sol+=v[a.front()];
    }
    fout<<sol;
    return 0;
}