#include <fstream>
#include <deque>
using namespace std;
ifstream f("intrare.in");
ofstream g("iesire.out");
const int nmax = 5000005;
deque<int> dq;
int a[nmax];
long long sum;
int n, k;
int main(){
    f >> n >> k;
    for(int i = 1; i <= n; i++){
        f >> a[i];
        while(!dq.empty() && a[dq.back()] >= a[i]){
            dq.pop_back();
        }
        dq.push_back(i);
        if(dq.front() <= i - k){
            dq.pop_front();
        }
        if(i >= k){
            sum += a[dq.front()];
        }
    }
    g << sum << '\n';
}