#include <iostream>
#include <fstream>
#include <deque>

using namespace std;

const int dim = 5e6 + 5;
int a[dim];
int n, k;
long long sol;

deque<int> dq;

int main(){
    ifstream cin("deque.in");
    ofstream cout("deque.out");
    cin >> n >> k;
    for(int i = 1; i <= n; i++){
        cin >> a[i];
    }
    for(int i = 1; i <= n; i++){
        while(!dq.empty() and a[dq.back()] >= a[i]){
            dq.pop_back();
        }
        dq.push_back(i);
        if(dq.front() <= i - k){
            dq.pop_front();
        }
        if(i >= k){
            sol += a[dq.front()];
        }
    }
    cout << sol;
    return 0;
}