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

const int maxn=5000009;
int i,N,K,A[maxn],D[maxn],Front,Back;
long long S;

int main()
{
	fin >> N >> K;
	for(i=1;i<=N;i++)
		fin >> A[i];
	Front=1; Back=0;
	for(i=1;i<=N;i++)
	{
		while(Front <= Back && A[D[Back]] >= A[i])
			Back--;
		D[++Back]=i;
		if(D[Front]==i-K) Front++;
		if(i>=K) S+=A[D[Front]];
	}
	fout << S;
}