#include <fstream>
#include <deque>
const int NMAX=5*1e6+5;
#define int long long

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

deque <signed> dq;
signed a[NMAX];

signed main()
{
    int i, ans=0, n, k;
    cin>>n>>k;
    for(i=1; i<=n; i++) cin>>a[i];
    for(i=1; i<=n; i++)
    {
        while(!dq.empty() && a[i]<a[dq.back()]) dq.pop_back();
        dq.push_back(i);
        while(!dq.empty() && (i-dq.front())>=k) dq.pop_front();
        ans+=a[dq.front()]*(i>=k);
    }
    cout<<ans<<'\n';
    return 0;
}