#include <bits/stdc++.h>

using namespace std;

int main()
{
    freopen("deque.in", "r", stdin);
    freopen("deque.out", "w", stdout);
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int n,k;
    cin>>n>>k;
    vector<int> v(n);
    deque<int> q;
    for (int i=0;i<n;i++){
        cin>>v[i];
    }
    for (int i=0;i<k;i++){
        while (!q.empty() && v[q.back()]>=v[i]){
            q.pop_back();
        }
        q.push_back(i);
    }
    long long ans=v[q.front()];
    for (int i=k;i<n;i++){
        while (!q.empty() && q.front()<i-k+1){
            q.pop_front();
        }
        while (!q.empty() && v[q.back()]>=v[i]){
            q.pop_back();
        }
        q.push_back(i);
        ans+=v[q.front()];
    }
    cout<<ans;
    return 0;
}