#include<fstream>
#include<deque>
using namespace std;

ifstream in("deque.in"); ofstream out("deque.out");

deque <int> coada;
int v[5000005];

int main (){

    int n, k;
    in >> n >> k;

    long long s = 0;

    for(int i = 1; i <= n; i++){
        in >> v[i];

        while(!coada.empty() && v[i] < v[coada.back()]) coada.pop_back();

        coada.push_back(i);

        if(i >= k){
            s += v[coada.front()];
            if(!coada.empty() && i - coada.front() + 1 >= k) coada.pop_front();
        }
    }
    out << s;
    return 0;
}