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

using namespace std;

int A[N],nr,n,i,k,li,ls;
long long 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",&A[i]);
    for (i=1; i<=k; i++)
    {
        while (!DQ.empty() && A[i]<=A[DQ.back()])
            DQ.pop_back();
        DQ.push_back(i);
    }
    sum=0;
    for (i=k+1; i<=n; i++)
    {
        sum+=A[DQ.front()];
        if (DQ.front()<=i-k) DQ.pop_front();
        while (!DQ.empty() && A[i]<=A[DQ.back()])
            DQ.pop_back();
        DQ.push_back(i);
    }
    printf("%lld",sum+A[DQ.front()]);

    return 0;
}