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

    }
    fout<<s;

    return 0;
}