#include <fstream>
#define N 5000001
#include <deque>
std::ifstream fin("deque.in");
std::ofstream fout("deque.out");
int n, k, arr[N];
std::deque<int> D;
int main(){
    fin >> n >> k;
    for(int i = 1; i <= n; i++){
        fin >> arr[i];
    }
    int64_t sum = 0;
    for(int i = 1; i <= n; i++){
        while(!D.empty() && arr[i] <= arr[D.back()]){
            D.pop_back();
        }
        D.push_back(i);
        if(i - k >= 1 && D.front() == i - k){
            D.pop_front();
        }
        if(i - k >= 0)
            sum += arr[D.front()];
    }
    fout << sum ;
}