#include <fstream>
#include <deque>
using namespace std;
ifstream cin("deque.in");
ofstream cout("deque.out");
const int MAX = 5e6 + 1;
int v[MAX], n, k;
deque<int> q;
int main()
{
    cin >> n >> k;
    for(int i = 1; i <= n; ++i) {
        cin >> v[i];
    }
    long long ans = 0;
    for(int i = 1; i <= n; ++i) {
        while(!q.empty() && v[ q.back() ] > v[i]) {
            q.pop_back();
        }
        q.push_back(i);
        if(q.front() == i - k) {
            q.pop_front();
        }
        if(i >= k) {
            ans = ans + v[ q.front() ];
        }
    }
    cout << ans;
}