#include <cstdio>
#include <deque>
#define mx 5000001
#define pb(i) push_back(i);
using namespace std;
int n,k,i,j,a[mx];
long long suma=0;
deque <int> v;
int main()
{	freopen("deque.in","r",stdin);
	freopen("deque.out","w",stdout);
	scanf("%d %d",&n,&k);
    for(i=1;i<=n;++i)
    {scanf("%d",&a[i]);
        while (v.size()&&a[i]<=a[v.back()])v.pop_back();
        v.pb(i);
         if (v.front()==i-k) v.pop_front();
        if (i>=k) suma+=a[v.front()];
    }
    printf("%lld",suma);
    return 0;
}