#include <fstream>
#include <deque>
#define ll long long

using namespace std;

ifstream cin("deque.in");
ofstream cout("deque.out");

const int NMAX = 5e6;
int n, x, k;
ll v[NMAX + 5], ans;
deque <int> d;


int main(){

    cin >> n >> k;
    
    for(int i = 1; i <= n; i++){
        
        cin >> v[i];

        if(!d.empty() && d.front() == i - k)
            d.pop_front();

        while(!d.empty() && v[d.back()] >= v[i])
            d.pop_back();

        d.push_back(i);

        if(i >= k)
            ans += v[d.front()];
        
    }

    cout << ans;

    return 0;
}