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

int n, k;
long long sum = 0;
deque<int> dq;
int v[5000005];
int main()
{
    ifstream cin("deque.in");
    ofstream cout("deque.out");
    cin >> n >> k;
    cin >> v[1];
    dq.push_front(1);
    for(int i = 2; i<=n; i++){
        cin >> v[i];
        while(!dq.empty() && v[dq.back()] >= v[i] ){ //scot toate mai mari
            dq.pop_back();
        }
        dq.push_back(i);
        while(i - dq.front() + 1 > k){ //scot toate care nu mai sunt in secv
            dq.pop_front();
        }
        if(i >= k)sum +=v[ dq.front()]; // adaug la min

    }
    cout << sum;

    return 0;
}