#include <fstream>
#include <deque>

using namespace std;

long long a[5000005];
deque <long long> dq;

int main(){
    int n,k,i;
    long long sum=0;
    ifstream f("deque.in");
    ofstream g("deque.out");

    f>>n>>k;
    for(i = 1 ; i <= n; ++i) f>>a[i];

    for(i = 1 ; i <= n; ++i){

        while(!dq.empty() && a[i]<= dq.back() ){

            dq.pop_back();
        }

        dq.push_back(a[i]);
        if(a[i-k] == dq.front()) dq.pop_front();
        if(i >= k) {
            sum += dq.front();
        }


    }
    g<<sum;


}