#include <fstream>
#include <deque>

using namespace std;

ifstream in("deque.in");
ofstream out("deque.out");

const int MAX = 5e6+1;
deque<int> q;
int n, k, v[MAX];
long long ans;

int main()
{
    in>>n>>k;
    for(int i=1; i<=n; i++)
        in>>v[i];
    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+=v[q.front()];
    }
    out<<ans;
    return 0;
}