#include <fstream>
#include <deque>

using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
int n, m, i, a[5000005], sum = 0, k;
deque <int > dq;
int main()
{
    f >> n >>  k;
    for( i = 1 ; i<=n; i++)
    f >> a[i];
    for(i=1; i<=n; i++)
    {
        while ( !dq.empty() && a[i] <= a[dq.back()])
            dq.pop_back();
            dq.push_back(i);
        if( dq.front() == i-k)
            dq.pop_front();
        if ( i >= k )
            sum += a[dq.front()];
    }
    g << sum;
    return 0;
}