#include<stdio.h>
#include<deque>
using namespace std;
int n,k,i,x[5000005];
long long s;
deque<int> q;
FILE *f;
int main(){
	f=fopen("deque.in","r");
	fscanf(f,"%d%d",&n,&k);
	for(i=1;i<=n;i++)
		fscanf(f,"%d",&x[i]);
	fclose(f);
	for(i=1;i<=n;i++){
		while(!q.empty()&&x[i]<=x[q.back()])
			q.pop_back();
		q.push_back(i);
		while(q.front()<=i-k)
			q.pop_front();
		if(i>=k)
		s+=x[q.front()];
	}
	f=fopen("deque.out","w");
	fprintf(f,"%lld\n",s);
	fclose(f);
	return 0;
}