#include<cstdio>
#include<deque>
using namespace std;
int k,i,n,a[5000003];
long long s;
deque < int > b;
int main()
{
freopen("deque.in","r",stdin);
freopen("deque.out","w",stdout);
scanf("%d",&n);
scanf("%d",&k);
for(i=1;i<=n;i++)
	scanf("%d",&a[i]);
s=0;
for(i=1;i<=n;i++)
{
	while(!b.empty()&&a[b.back()]>=a[i]) b.pop_back();
	b.push_back(i);
	if(i-b.front()+1>k) b.pop_front();
	if(i>=k) s=s+a[b.front()];
}
printf("%d\n",s);
return 0;
}