#include <fstream>
#define N 5000000

using namespace std;
ifstream cin("deque.in");
ofstream cout("deque.out");
int coada[N], v[N];
int main(){
    int n, k;
    cin >> n >> k;
    for(int i = 1; i <= n; i++)
        cin >> v[i];
    int inc = 1, sf = 1;
    long long suma = 0;
    coada[inc] = 1;
    for (int i = 2; i <= n; i++){
        if (v[i] > v[coada[sf]]){
            sf++;
            coada[sf] = i;
        }
        else{
            while (inc <= sf && v[coada[sf]] >= v[i])
                sf--;
            sf++;
            coada[sf] = i;
        }
        while (coada[sf] - coada[inc] >= k && sf - inc >= 0)
            inc++;
        if (i >= k)
            suma += v[coada[inc]];
    }
    cout << suma;
    return 0;
}