#include <fstream>
#include <deque>
using namespace std;
ifstream fin ("deque.in");
ofstream fout("deque.out");
int v[ 5000005];
deque<int> q;

int main()
{
    long long int i,x,n,s,t;
    long long int total=0;
    fin>>n>>t;
    for(i=1; i<=n;i++)
        fin>>v[i];

    q.push_front(1);
    for(i=2;i<=n;i++)
    {
        if(q.empty()) q.push_front(i);
        while(i-q.front()>=t)
            q.pop_front();
        while(!q.empty() && v[q.back()]>= v[i])
            q.pop_back();
        q.push_back(i);
        if(i>=t)total+=v[q.front()];
    }
    fout<<total;
    return 0;
}