#include <deque>
#include <fstream>
#define LL long long

using namespace std;

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

const int N=5e6+2;

deque<LL> dq;
LL n,k,sum,i;
int v[N];

int main()
{
    fin>>n>>k;
    for(i=1; i<=n; i++)
    {
        fin>>v[i];
        while(!dq.empty() && v[dq.back()]>=v[i])
            dq.pop_back();
        dq.push_back(i);

        if(i-dq.front()==k)
            dq.pop_front();
        if(i>=k)
            sum+=v[dq.front()];
    }
    fout<<sum<<'\n';
    return 0 ;
}