#include<cstdio>
#include<deque>
using namespace std;
deque<int> d;
long int n,i,k,v[5000005];
long long s;
int main()
{
	freopen("deque.in","r",stdin);
	freopen("deque.out","w",stdout);
	scanf("%ld %ld",&n,&k);
	for(i=1;i<=n;i++){
		scanf("%ld",&v[i]);
		while(!d.empty() && v[d.back()]>v[i])d.pop_back();
		d.push_back(i);
		if(d.front()<=i-k)d.pop_front();
		if(i>=k)s=s+v[d.front()];
	}
	printf("%lld",s);
	return 0;
}