#include <bits/stdc++.h>
#define int long long

using namespace std;
unsigned int v[5000000];
deque<int> dq;
int32_t main()
{
    ifstream cin("deque.in");
    ofstream cout("deque.out");
    int n, k, sum=0;
    cin>>n>>k;

    for(int i=1;i<=n;i++)
    {
        cin>>v[i];
        while(dq.empty() == false && v[dq.back()] >= v[i])
            dq.pop_back();

        dq.push_back(i);

        if(dq.front() <= i - k)
            dq.pop_front();

        if(i >= k)
            sum += v[dq.front()];
    }

    cout<<sum;


    return 0;
}