#include <bits/stdc++.h>
using namespace std;
deque<int> dq;
int v[5000002];
int main()
{
    ifstream cin("deque.in");
    ofstream cout("deque.out");
    int n,k;
    long long ans=0;
    cin >> n >> k;
    for(int i=1;i<=n;i++)
        cin >> v[i];
    for(int i=1;i<=n;i++){
        while(!dq.empty() && v[dq.back()]>v[i]){
            dq.pop_back();
        }
        while(!dq.empty() && dq.front()<=i-k)
            dq.pop_front();
        dq.push_back(i);
        if(i>=k)
            ans+=v[dq.front()];
    }
    cout << ans;
    return 0;
}