#include <cstdio>
#include <deque>
#define N 5000001

using namespace std;

int A[N],n,k,i,sum;
deque<int> DQ;

int main()
{
	freopen("deque.in","r",stdin);
	freopen("deque.out","w",stdout);
	scanf("%d%d\n",&n,&k);
    for (i=1; i<=n; i++) scanf("%d\n",&A[i]);
    sum=0;
    for (i=1; i<=n; i++)
    {
        while (!DQ.empty() && A[i]<=A[DQ.back()])
            DQ.pop_back();
        DQ.push_back(i);
        if (DQ.front()<=i-k)
            DQ.pop_front();
        if (i>=k)
            sum+=A[DQ.front()];
    }

    printf("%d",sum);

    return 0;
}