#include<fstream>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");

int n,k, v[5000001];
int dq[5000001];
int p,u;
long long s=0;

int main()
{ 
	int i;
	fin>>n>>k;
	for(i=1;i<=n;i++)
		fin>>v[i];
    
	u=0;
	p=1;
	for(i=1;i<=n;i++)
	{
		while(p<=u&&v[i]<=v[dq[u]])u--;
		dq[++u]=i;
		if(dq[p]<=i-k)p++;
		if(i>=k)s+=v[dq[p]];
	}
	fout<<s;
return 0;
}