#include <stdio.h>
#include <queue>
using namespace std;

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