#include <cstdio>
#include <deque>
using namespace std;
deque < int > q;
int i,j,n,m,k,x,a[5000005];
long long s;
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]);
        if(q.empty()) {q.push_back(i);continue;}
        if(a[i]<a[q.front()]) q.push_front(i);
        else
        {
            if(!q.empty())
            while(a[q.back()]>=a[i])
            q.pop_back();
            q.push_back(i);
        }
        if(i>=k)
        {
            while(q.front()<=i-k)
             q.pop_front();
            s+=a[q.front()];
    }}
    printf("%d\n",s);

    return 0;
}