#include <fstream>
#include <deque>
#define NMAX 5000001

using namespace std;

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

deque <int> q;
long long s;
int N, K, a[NMAX];

int main()
{
    fin>>N>>K;

    for(int i=1; i<=N; ++i)
        fin>>a[i];

    for(int i = 1; i <= N; i++)
    {
        while(!q.empty() && a[q.back()] >= a[i])
            q.pop_back();

        q.push_back(i);

        if(i - q.front() == K) q.pop_front();
        if(i >= K) s += a[q.front()];
    }

    fout<<s;

    return 0;
}