#include <fstream>
#include <deque>

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

deque<int> dq;
int v[5000001];
int main()
{
    ///min1<min2
    int n, k, sum=0;
    cin>>n>>k;
    for(int i=0; i<n; i++) cin>>v[i];

    for(int i=0; i<n; i++)
    {
        while(!dq.empty() && v[dq.back()]>=v[i])
            dq.pop_back();

        dq.push_back(i);

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

        if(i>=k-1)
            sum+=v[dq.front()];
    }
    cout<<sum;
    return 0;
}
/*
9 3
-7 9 2 4 -1 5 6 7 1
*/