#include <fstream>
#include <deque>
using namespace std;
ifstream fin( "deque.in" );
ofstream fout( "deque.out" );
const int NMAX = 5e6;
int v[NMAX + 2];
deque <int> dq;
int main()
{
    int n, k, i, s;
    fin >> n >> k;
    for( i = 1; i <= n; ++i )
        fin >> v[i];
    s = 0;
    for( i = 1; i <= n; ++i )
    {
        while( !dq.empty() && v[i] <= v[dq.back()] )
            dq.pop_back();
        dq.push_back(i);
        if( dq.front() == i - k )
            dq.pop_front();
        if( i >= k )
            s += v[dq.front()];
    }
    fout << s;
    return 0;
}