#include <fstream>
#include <deque>
using namespace std;
ifstream cin("deque.in");
ofstream cout("deque.out");
int v[5000001];
deque <int> d;
int main()
{

    int n,k,i;
    long long s=0;
    cin>>n>>k;
    for(i=1;i<=n;i++)
        cin>>v[i];
    for(i=1;i<=n;i++){
        while(d.empty()==false && v[d.back()]>=v[i])
            d.pop_back();
        d.push_back(i);
        if(i>=k){
            if(d.empty()==false && d.front()<=i-k)
                d.pop_front();
            s+=v[d.front()];
        }
    }
    cout<<s;

    return 0;
}