#include <fstream>
#define NMAX 5000002

using namespace std;

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

int N,K;
int Deque[NMAX],S,F;
int V[NMAX];

long long Sum;

int main()
{
    int i;
    in>>N>>K;
    for(i=1;i<=N;i++)
    {
        in>>V[i];
        while(i - Deque[S] >=K)
            ++S;
        while(F>=S&&V[i] <= V[Deque[F]])
            F--;
        Deque[++F] = i;
        if(i>=K)
            Sum += V[Deque[S]];
    }
    out<<Sum<<'\n';
    return 0;
}