#include <cstdio>
#include <deque>
using namespace std;
const int NMax=5000002;

deque <int> D;
int N,K,v[NMax];
long long sum;

int main(){
	freopen("deque.in","r",stdin);
	freopen("deque.out","w",stdout);
	scanf("%d%d",&N,&K);
	int i;
	for(i=1;i<=N;++i){
		scanf("%d",v+i);
	}
	for(i=1;i<K;++i){
		for(;!D.empty() && v[D.back()]>=v[i];D.pop_back()){}
		D.push_back(i);
	}
	for(;i<=N;++i){
		for(;!D.empty() && v[D.back()]>=v[i];D.pop_back()){}
		D.push_back(i);
		if(D.front()<=i-K){
			D.pop_front();
		}
		sum+=v[D.front()];
	}
	printf("%lld",sum);
	return 0;
}