#include <fstream>
#include <deque>

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

long long n,k,i,x,s,v[5000005];
deque <int> dq;

int main()
{
    fin>>n>>k;
    for(i=1;i<=n;i++){
        fin>>v[i];
        while(!dq.empty() && v[i]<v[dq.back()])
            dq.pop_back();
        dq.push_back(i);
        while(!dq.empty() && i-dq.front()>=k)
            dq.pop_front();
        if(i>=k)
            s+=v[dq.front()];
    }
    fout<<s;
    return 0;
}